--- title: "Online Coding and Python Classes in Crosby | AI, Ages 6 to 67" description: "Python, coding, AI and vibe coding taught live online for Crosby, Blundellsands, Waterloo, Thornton and Hightown learners aged 6 to 67. Free first lesson." canonical: https://learn.modernagecoders.com/online-coding-and-python-classes-in-crosby source: src/pages/online-coding-and-python-classes-in-crosby.html --- > Python, coding, AI and vibe coding taught live online for Crosby, Blundellsands, Waterloo, Thornton and Hightown learners aged 6 to 67. Free first lesson. Skip to contentCourses to start with ## Python and coding routes for Crosby learners Four ways in, depending on age. Each starts with a live lesson at no charge, with no card requested. [![Python and AI for Kids course thumbnail](/images/python-kids.webp)Ages 9 to 13Python and AI for KidsFirst real Python for children, with small AI projects and plenty of dice, coins and random numbers.See the syllabus](/courses/python-ai-kids-masterclass)[![Problem Solving and Computational Thinking for Kids course thumbnail](/images/problem-solving-kids.webp)Ages 7 to 12Problem Solving and Computational Thinking for KidsHow to think before you code: fair choices, counting steps and spotting a quicker method.See the syllabus](/courses/problem-solving-and-computational-thinking-for-kids)[![Python for Teens course thumbnail](/images/python-teens.webp)Ages 13 to 17Python for TeensThe full Python course for teenagers, lists to algorithms, with the Crosby sampling experiment inside.See the syllabus](/courses/python-complete-masterclass-teens)[![Data Structures & Algorithms Course course thumbnail](/images/dsa-college.webp)Students and adultsData Structures & Algorithms CourseData structures and algorithms with the costs counted, for university, interviews or work.See the syllabus](/courses/data-structures-algorithms-masterclass-college) Browse the [course atlas](/course-atlas) for more than one hundred options and use the [coding roadmap](/coding-roadmap) to check prerequisites. The four we are known for ### Python, AI, vibe coding and agentic coding These run underneath everything above. Every one is live and online, placed by ability rather than by age, and the first class is free. [![Vibe Coding for Teens course thumbnail](/images/vibe-coding-teens.webp)Vibe codingAges 13 to 17Vibe Coding for TeensPython, web and AI projects where the learner still owns the thinking.See the syllabus](/courses/vibe-coding-for-teens-python-web-ai-projects-course)[![Python Automation Course course thumbnail](/images/python-college.webp)Python and AICollege and adultPython Automation CourseAutomate the work you already do, then let AI carry part of it.See the syllabus](/courses/python-ai-automation-masterclass-college)[![AI and Machine Learning for Teens course thumbnail](/images/ai-ml-teens.webp)AI and MLAges 14 to 18AI and Machine Learning for TeensTrain a model, read what it learned, and be able to say why it is wrong.See the syllabus](/courses/ai-ml-masterclass-teens)[![Codex & Claude Code course thumbnail](/images/codex-claude-code-adults.webp)Agentic codingProfessionalsCodex & Claude CodeRun AI coding agents on real work without losing control of the codebase.See the syllabus](/courses/codex-and-claude-code-ai-coding-agents-masterclass-for-adults-professionals)Crosby on the record ## Crosby, Blundellsands, Waterloo, Thornton and Hightown The published census counts, and how the gazetteer describes the places around the town. | Area | Usual residents | | --- | --- | | Crosby built-up area | 50,215 | | Sefton borough | 279,233 | Each figure is published in its own right. The borough count takes in several other towns, so the two rows are not parts of one sum. postcodes.io records Great Crosby, Blundellsands and Thornton as suburban areas in the L23 district, Waterloo as a suburban area in L22, Little Crosby as an L23 village and Hightown as a village in L38, all within Sefton. Crosby schools teach the national curriculum for England. We place children by school year, from Year 2 to Year 13, and can keep pace with GCSE and A level computer science and maths. ### More Merseyside pages Try [coding classes in Merseyside](/coding-classes-in-merseyside), [Bootle](/ai-and-programming-classes-in-bootle) and [Southport](/best-coding-and-ai-classes-in-southport). For the thinking behind our teaching, read [learn to think, not just use AI tools](/learn-to-think-not-just-use-ai-tools-uk). The Crosby project ## Weighted random choice and the alias method Pick a Crosby resident at random. Which small census area are they in? The census divides the country into output areas, small patches of a few streets each. The Crosby built-up area is made of 169 of them, and the 2021 count of residents in each one runs from 129 to 546. The learner's job is to write a Python function that returns the area of a randomly chosen resident. An area with 546 people should come up more than four times as often as one with 129. We use the area counts only as weights. Their sum is our own working figure, not an official population; the published figure for the town is the 50,215 above. The first attempt most people write is wrong: pick one of the 169 areas with equal chance. Over a million draws that gave the largest area 5,879 picks when its fair share is 10,873, and gave the smallest 5,842 when it is due 2,569. Every area is treated alike, so residents of crowded areas are under-counted. The fix is to weight the choice, and there are three ways to do it. | Method | Comparisons per draw | Set-up work | | --- | --- | --- | | Walk down the running totals | 86.3 on average | One pass to add up | | Binary search the running totals (bisect) | 7.51 on average | One pass to add up | | Alias table | 1, always | 168 pairing steps | The walk is the obvious method: draw a random number up to the total and step through the list until the running total passes it, 86.3 comparisons on average. Sorting the areas largest first only trims that to 75.3, because the areas are all much the same size. Binary search halves the list each time and needs 7.51. The alias method changes the picture. Imagine 169 equal columns, one per area. Areas with more than the average spill their extra into the columns of areas with less, until every column is full and holds at most two areas: its owner and one alias. Building that table took 168 pairing steps. After that, a draw is one random column and one comparison to decide between owner and alias, no matter how many areas there are. Fast is no use if it is unfair, so the learner checks. Per million draws the largest area should appear 10,873 times and the alias table gave 10,899; the smallest should appear 2,569 times and got 2,539. A chi-square test across all 169 areas scored 184.6 for the alias table and 166.1 for binary search, both ordinary values for 168 degrees of freedom, against 48,808 for the wrong uniform method. One more result surprises people: the area of a random resident holds 310.0 people on average, while a random area holds 297.1. Sampling by person tilts you towards bigger areas. ### Ages 8 to 11 Make a spinner with unequal slices, then a fair-looking one with two colours per slice, and compare tallies. ### Ages 11 to 15 Write the running-total walk in Python, count its comparisons, then swap in bisect. ### Ages 15 and up Build the alias table, prove each column sums to one share, and test a million draws for fairness. ### About the data Census 2021 output-area counts are from the Office for National Statistics through Nomis, read 30 September 2026, under the Open Government Licence. The sampling methods, the comparison counts and the checks are our own work with a fixed random seed; a different seed would move the tallies slightly. Randomness inside AI ## What weighted sampling has to do with AI, vibe coding and agents Each word a language model writes is usually a weighted random draw. | In the Crosby experiment | In AI and software | | --- | --- | | Uniform choice gave 5,879 where 10,873 were due | A plausible shortcut can be quietly biased | | The walk needed 86.3 comparisons | The first method that works may not scale | | The alias table needed 1 | Set-up work can buy very fast answers | | Tallies were tested against fair shares | Random code needs a statistical test, not a glance | | A fixed seed made runs repeatable | Reproducible randomness makes bugs findable | A large language model gives a score to every possible next token, turns the scores into probabilities and then, in its usual settings, draws one at random according to those probabilities. That is the Crosby task with tens of thousands of options in place of 169, repeated for every word. Training data is sampled with weights too, and so are the moves in many game-playing programs. In vibe coding, where you describe a program in plain English and an AI writes it, a request for "a random choice" may come back as the uniform version, which runs without error and gives unfair results. Learners who have counted the tallies themselves know to ask for weights and to test the output. An AI agent that samples options or retries tasks needs the same care. We introduce agent building once a learner's Python is secure, generally in the later teenage years or as an adult, and we teach Copilot Studio agents only in one-to-one lessons. Further reading: [understand the code, don't copy-paste](/understand-the-code-dont-copy-paste-uk) and [the AI agents course for UK students](/ai-agents-course-for-students-uk). The Office for National Statistics, Nomis and postcodes.io have no link to Modern Age Coders. Their open data made the project possible; the sums and conclusions are our responsibility. The route up ## Spinners first, then Python, then algorithms School year gives us a first guess at the level. One free lesson settles it. Years 2 to 6 ### How to think Fair and unfair games, tallies and patterns, on paper and in Scratch. [Problem Solving and Computational Thinking for Kids](/courses/problem-solving-and-computational-thinking-for-kids)[Scratch Coding for Kids](/courses/scratch-programming-complete-course)Years 5 to 8 ### First Python Typed code from day one, with an AI helper the child learns to question. [Python and AI for Kids](/courses/python-ai-kids-masterclass)[Vibe Coding for Kids](/courses/vibe-coding-for-kids-beginners-ai-scratch-game-dev)Years 9 to 13 ### Python in depth Lists, random, bisect and testing, alongside GCSE and A level. [Python for Teens](/courses/python-complete-masterclass-teens)[Vibe Coding for Teens](/courses/vibe-coding-for-teens-python-web-ai-projects-course)Adults ### Algorithms and AI Efficient methods, probability and machine learning for study or a career move. [Data Structures & Algorithms Course](/courses/data-structures-algorithms-masterclass-college)[Python Masterclass](/courses/python-programming-masterclass-zero-to-advanced-college)Python and AI ## What is the alias method, and how does AI pick its next word? The alias method is a way of drawing a random item from a weighted list in one step by first rearranging the weights into equal columns that each hold at most two items, and a language model usually picks its next word by just such a weighted random draw, over probabilities computed from its scores. Across 169 Crosby output areas, the running-total walk took 86.3 comparisons per draw, binary search 7.51 and the alias table one. The careless uniform version handed the largest area 5,879 picks per million where it should have had 10,873, and nothing in the program complained. Seeing that for themselves is why Crosby teenagers who code can still check an AI's work in 2026 instead of trusting it. The longer argument is in [why teenagers should still learn to code in 2026](/blog/is-coding-worth-learning-2026). Practicalities ## What a Crosby lesson looks like We teach by video call. A computer with a camera and microphone is all a learner needs, plus a spot at home where they can concentrate. ### Hands on keys The learner writes the code on a shared screen while the tutor guides with questions. ### Try before deciding A complete free lesson lets us see the learner at work and recommend a course. ### No card for the trial Booking it needs a name, an age and a phone number. ### Same-level groups Classes of five to ten, matched by stage and joined from all over the UK. ### Twice a week in term With breaks for Sefton school holidays when you let us know the dates. ### Fixed UK times When clocks go forward or back, our tutors adjust and your slot does not. Why we teach online On a shared screen the tutor sees every keystroke, and a national pool of learners lets us form classes at one precise level. Fees ## Crosby lesson fees Learners anywhere outside India pay the same international rates. First class**USD 0** The opening lesson is free and complete, with course advice at the end. Group tuition**USD 100** Five to ten learners in a class, roughly eight lessons per month. Private tuition**USD 150** One-to-one with a tutor, roughly eight lessons per month. Fees are stated in US dollars and we give no price in pounds. Nothing is charged until the trial is done and you have settled on a course and a time. See the pricing page for holiday breaks, absences and switching format. Request placement[Check availability](https://wa.me/919123366161?text=Hello%20Modern%20Age%20Coders%2C%20I%20am%20looking%20for%20a%20free%20Python%20or%20coding%20lesson%20for%20a%20learner%20in%20Crosby.)Reviews ## Google reviews from Merseyside families and learners around the UK Rated 4.9 across 547 Google reviews. These are real reviews, reproduced as written. ★★★★★ "The one step solution for my son. Modern Age Coders make learning coding so simple that kids love it. The teachers explain complex concepts clearly with practical exercises and interactive content." Ria Mukherjee Parent ★★★★★ "Modern Age Coders has been a game-changer for me. I struggled to grasp IT concepts and coding before joining, but their classes transformed everything. I can now confidently write complex programs with ease." Samriddha Mondal Student ★★★★★ "One of the most wonderful education centres out there. Education is not limited to school syllabus but focuses on skill development." Vansh Agarwal Student ★★★★★ "My child Dhairya is really enjoying the Modern Age Coders classes. This is his first online class and he eagerly looks forward to it. I can already see his improvement, and the teachers are very cooperative." Sonam Oswal Parent of Dhairya ★★★★★ "Modern Age Coders have wonderful teachers who teach in a clear, easy and practical way. The teacher boosts students' confidence and inspires them to learn without hesitation." Sonu Goyal Parent ★★★★★ "I highly recommend this computer coding class! The teachers are incredibly knowledgeable and passionate about coding." Ritu Kedia Parent Free placement class ## Ask for a free Crosby lesson Let us know the learner's age or school year and one interest. A first lesson could be an unfair spinner to investigate, a Scratch game made with AI help, a few lines of Python, or a random draw to test. ### Want a class sooner? Book a priority demo A priority demo is a full class of about 45 to 60 minutes. After the class the mentor sends a written skill report and a personal learning roadmap on WhatsApp. If you enrol, the demo fee is adjusted against your first month's fee. Share your demo Order ID with us on WhatsApp and we take it off. [Book a priority demo](/book-demo) ### Contact the team directly WhatsApp or call [+91 91233 66161](tel:+919123366161), or email [connect@modernagecoders.com](mailto:connect@modernagecoders.com). This is Modern Age Coders' actual contact, an Indian number, and not an invented Crosby one. [WhatsApp Modern Age Coders](https://wa.me/919123366161?text=Hello%20Modern%20Age%20Coders%2C%20I%20am%20looking%20for%20a%20free%20Python%20or%20coding%20lesson%20for%20a%20learner%20in%20Crosby.) Submitted details are used for placement and follow-up. FAQ ## Questions from Crosby Random choice, the census experiment, Python, vibe coding and how lessons are arranged. ### What is the population of Crosby? The ONS figure for the Crosby built-up area at the 2021 census is 50,215 usual residents. Sefton borough had 279,233. ### Can I learn Python online from Crosby? Yes. We teach Python live online to ages 6 to 67 in Crosby, Blundellsands, Waterloo, Thornton, Little Crosby and Hightown. ### What is the alias method? It is a technique for choosing a random item from a weighted list in constant time, using a prepared table in which each column holds at most two items. ### What is weighted random sampling? It is choosing at random so that each option's chance matches its weight, so an option with twice the weight is picked twice as often. ### What did the Crosby project measure? Over 169 output areas, a linear walk used 86.3 comparisons per draw, binary search 7.51 and the alias table one, with all three passing a fairness test. ### Is vibe coding part of the course? Yes. Learners ask an AI for code in plain English, then read it, test it and fix what is wrong. ### When do learners start building AI agents? After they can write Python confidently, usually older teenagers and adults. Copilot Studio agents are taught one-to-one only. ### Will this support GCSE or A level? The programming, algorithms and probability all appear in those courses. We build understanding and never promise a grade. ### What does it cost? Nothing for the first lesson. After that, USD 100 a month in a group or USD 150 a month one-to-one. ### Can lessons pause for holidays? Yes, send the dates and we will stop for them. Next ## Other towns in Merseyside Each page has a project of its own: [Bootle](/ai-and-programming-classes-in-bootle) (how much data a model needs), [Southport](/best-coding-and-ai-classes-in-southport) (how AI splits words into tokens) and [Liverpool](/best-coding-class-in-liverpool). There is more on the [North West England page](/coding-and-ai-classes-in-north-west-england) and the [UK hub](/coding-classes-in-united-kingdom). Book the free class[Book a priority demo](/book-demo)[Chat with us on WhatsApp](https://wa.me/919123366161?text=Hello%20Modern%20Age%20Coders%2C%20I%20am%20looking%20for%20a%20free%20Python%20or%20coding%20lesson%20for%20a%20learner%20in%20Crosby.)Free class[Priority demo](/book-demo)[Call us](tel:+919123366161) ## Keep exploring Modern Age Coders ### Related courses and guides - [Online Coding and Python Classes in Cumbernauld](/online-coding-and-python-classes-in-cumbernauld) - [Online Coding and Python Classes in Crawley](/online-coding-and-python-classes-in-crawley) - [Online Coding and Python Classes in Didsbury, Manchester](/online-coding-and-python-classes-in-didsbury-manchester) - [Online Coding and Python Classes in Corby](/online-coding-and-python-classes-in-corby) - [Online Coding and Python Classes in Downpatrick](/online-coding-and-python-classes-in-downpatrick) - [Online Coding and Python Classes in Colwyn Bay](/online-coding-and-python-classes-in-colwyn-bay) - [Online Coding and Python Classes in Kingswood](/online-coding-and-python-classes-in-kingswood-bristol) - [Online Coding and Python Classes in Stourbridge](/online-coding-and-python-classes-in-stourbridge) - [Online Coding and Python Classes in Kingswinford](/online-coding-and-python-classes-in-kingswinford) ### Learn more - [AI and Python Academy for Girls in Ireland](/ai-and-python-academy-for-girls-ireland) - [AI and Python Classes for Girls in the UK](/ai-and-python-academy-for-girls-uk) - [Best Coding Classes in Reading](/best-coding-class-in-reading) - [Coding Classes in Lucan, Dublin](/coding-classes-in-lucan-dublin) ### Free resources - [Python Tutorial for Beginners: Complete Guide](/resources/python) - [Inheritance and Polymorphism](/resources/python/inheritance-and-polymorphism) - [Comprehensions and Generators](/resources/python/list-comprehensions-and-generators) - [Modules and Packages in Python](/resources/python/modules-and-packages) ### From the blog - [Python Tutorials & Guides](/blog/topic/python) - [Python OOP Tutorial: Classes, Objects, and Inheritance](/blog/python-oop-tutorial-for-beginners) - [How Do Spam Filters Work? Build a Simple One in Python](/blog/how-do-spam-filters-work) - [How to Find HCF and LCM in Python (5 Easy Methods)](/blog/how-to-find-hcf-and-lcm-in-python) ### Start here - [Try a free trial class with a Modern Age Coders mentor](/free-trial) - [About Modern Age Coders, teaching since 2020](/about) --- *Canonical: https://learn.modernagecoders.com/online-coding-and-python-classes-in-crosby*