How Does a Social Media Algorithm Decide What You See? A CS Unplugged Activity
A hands-on classroom activity where students simulate a social media feed algorithm using cards — no screens required. Covers algorithms, filter bubbles, data ethics and engagement-based design.
Gareth Edgell
Head of CS · Senior Examiner · 15+ years tutoring
The UK government has just announced a ban on social media for under-16s. But before we talk about whether that is right or wrong — do your students actually know how social media decides what appears on their screen?
It is not random. It is not chronological. It is an algorithm — and understanding how it works is one of the most important things a young person can learn about the digital world.
This unplugged activity lets students simulate a social media feed algorithm without a screen, a phone, or an account. Just cards, people, and some surprisingly tricky decisions.
It connects directly to the GCSE and A Level Computer Science curriculum, and works brilliantly as a discussion starter on digital ethics, AI, and the social effects of computing.
What You Need
- A pack of 20 cards (index cards work well), each representing a piece of content — write a brief description on each: a funny video, a news story, an advert, a post from a friend, a political opinion, a celebrity photo
- Sticky labels or coloured dots to represent user preferences
- A small group of 4–6 students (works equally well as a whole-class activity)
- Approximately 30–45 minutes
The Activity
Round 1 — Chronological Feed (5 minutes)
Shuffle the cards and deal them out in order. Everyone sees the same content in the same sequence. This is how social media used to work in the early days.
Discuss:
- Is this fair? Is it useful?
- What are the problems with showing everyone the same thing in the same order?
Round 2 — Introducing Weights (10 minutes)
Assign each student a profile: one person loves sport, one loves music, one is interested in politics, one just wants to see friends’ posts. Give each card a score from 1–3 for how relevant it is to each profile.
Each student now sorts their cards by score, highest first. This is their personalised feed.
Discuss:
- How did the feeds differ between students?
- Who decided what scored highly? Who wrote those rules?
- Could the scoring system ever be unfair?
Round 3 — The Engagement Trap (10 minutes)
Remove the scoring system entirely. Instead, students must now choose which cards they would stop and look at — which ones grab their attention. Mark those cards.
Reshuffle and deal again — but this time, cards that were previously marked get dealt first.
Discuss:
- What kinds of content kept getting promoted?
- Was it the most accurate content? The most useful? The most extreme?
- Who benefits from keeping you engaged?
What Just Happened?
Students just simulated the core mechanism behind every major social media platform.
The algorithm does not show users what is true, or what is good for them. It shows what keeps them looking — because every second spent on the platform is a second it can show an advert.
This is called an engagement-based algorithm. The more a user interacts with a type of content, the more of it they see. Over time the feed narrows — a phenomenon called a filter bubble — until it is mostly showing content that confirms what the user already thinks and feels.
The underlying process is a feedback loop: behaviour shapes the algorithm, the algorithm shapes behaviour, and so on.
The Big Discussion Questions
These work well as a written reflection, class debate, or homework task:
- Who is responsible for what the algorithm promotes — the platform, the users, or both?
- Could you design a fairer algorithm? What would you optimise for instead of engagement?
- Should algorithms be transparent — should users be able to see why they are being shown something?
- The UK government has announced a ban on social media for under-16s. Is understanding how algorithms work a better solution, a worse one, or something that should happen alongside the ban?
Curriculum Links
This activity connects to several areas of the GCSE and A Level Computer Science curriculum:
| Topic | Connection |
|---|---|
| Algorithms | How rules and conditions produce outputs from inputs |
| Data and its uses | How platforms collect and act on behavioural data |
| Ethical and legal issues | Who is responsible for algorithmic outputs |
| Artificial intelligence | How machine learning refines recommendations over time |
| Social effects of computing | Filter bubbles, misinformation, and platform design |
It also links to PSHE and citizenship curricula for schools looking for cross-curricular opportunities.
Extension Activities
For GCSE students: Ask students to write pseudocode for a simple recommendation algorithm that takes user history as input and outputs a ranked feed.
For A Level students: Research and present on one of the following — the Facebook News Feed algorithm, YouTube’s recommendation system, or TikTok’s For You page. How do they differ? What are the ethical implications of each?
For all students: Ask them to spend one day noting every time an algorithm makes a decision for them — not just social media, but Netflix, Spotify, Google search results, maps. Discuss findings as a class.
Want to Explore Algorithms Further?
Try the free interactive tools at compscitutoring.com/tools — including an algorithm visualiser, binary converter, logic gate simulator, and LMC simulator. All free, no account needed.