Most educational apps don't work. Not "could be better." Not "work...
Carl Hendrick@C_Hendrick
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Dec 21, 2025
~2 min read
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Most educational apps don't work. Not "could be better." Not "work for some kids." They're architecturally incapable of producing reliable learning. Here's why 🧵
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Every engineering field has invariants; conditions that MUST hold for the system to function. Bridges must resist loads. Planes must generate lift. Circuits need closed paths. Violate them and you don't get a worse bridge. You get collapse.
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Instruction has invariants too. There are non-negotiable conditions for learning to occur reliably. Most educational apps violate these invariants while copying the SURFACE features of teaching; lessons, quizzes, progress bars etc. They look like effective instruction. They're not. What are these instructional invariants? Here are 3 examples:
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Instructional invariant 1: The target skill must be the only path to success.
If a task can be completed WITHOUT using the skill you're teaching, some learners will find that other path.
Example: A reading app shows "elephant" next to a picture of an elephant. Child taps correctly. But did they decode or just match the image? The app can't tell. The dashboard shows progress. For all intents and purposes, the learning never happened.
If a task can be completed WITHOUT using the skill you're teaching, some learners will find that other path.
Example: A reading app shows "elephant" next to a picture of an elephant. Child taps correctly. But did they decode or just match the image? The app can't tell. The dashboard shows progress. For all intents and purposes, the learning never happened.
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Instructional invariant 2: Mastery before progress.
Prerequisites aren't optional. Learners who advance with gaps will struggle with everything built on those gaps. This looks like "struggling with maths." It's actually "moved forward before ready."
Prerequisites aren't optional. Learners who advance with gaps will struggle with everything built on those gaps. This looks like "struggling with maths." It's actually "moved forward before ready."
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Invariant 3. Active response required. Learning requires retrieval, production, generation. Information that washes over a passive learner leaves almost no trace. Clicking "Next" after watching a video is not reliable learning.
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Most education apps love passive formats because they're low-friction. Users don't get frustrated. Session times stay high. Paying parents are happy. Many prioritise engagement streaks.
But session time ≠ learning time. An hour of clicking, watching, and recognising can involve almost zero actual cognitive application.
But session time ≠ learning time. An hour of clicking, watching, and recognising can involve almost zero actual cognitive application.
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Why do apps violate these invariants?
Because compliance conflicts with the metrics apps optimise for:
- Session time (effort = fatigue = shorter sessions)
- Completion rates (mastery gates = people get stuck)
- User satisfaction (real feedback feels harsh)
Because compliance conflicts with the metrics apps optimise for:
- Session time (effort = fatigue = shorter sessions)
- Completion rates (mastery gates = people get stuck)
- User satisfaction (real feedback feels harsh)
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Audit for any educational app:
- Can tasks be done without the target skill?
- Multiple new things at once?
- Can learners just skip ahead?
- Watching or actually producing?
- Real feedback or just "try again"?
- Does practice match the real performance?
Most apps fail most of these checks imo. That's why most apps don't produce reliable learning.
- Can tasks be done without the target skill?
- Multiple new things at once?
- Can learners just skip ahead?
- Watching or actually producing?
- Real feedback or just "try again"?
- Does practice match the real performance?
Most apps fail most of these checks imo. That's why most apps don't produce reliable learning.
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Educational apps typically confuse features with learning and tend to optimise for:
- Engagement
- Personalisation
- Smooth user experience
- Motivation
- Time-on-task
- Engagement
- Personalisation
- Smooth user experience
- Motivation
- Time-on-task
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Learning is a constrained process. It only occurs when certain conditions are met. These conditions don’t care whether instruction is delivered by a teacher, a parent or an app.
These conditions are instructional invariants: the non-negotiable constraints under which learning reliably occurs. You can innovate endlessly within them. You cannot design around them. 🧵
These conditions are instructional invariants: the non-negotiable constraints under which learning reliably occurs. You can innovate endlessly within them. You cannot design around them. 🧵
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ok I wrote this up into a post: carlhendrick.substack.com/p/why-most-edu…
