If you've shopped for a kids' learning app, you've probably seen the phrase 'mastery-based' a lot. It is doing a lot of work — and it means very different things in different places.
What it usually means
Most apps use 'mastery-based' to mean: the kid practices a topic until a certain percentage of correct answers in a row, then the system moves on. That's better than 'cover the textbook chapter and move on regardless', but it leaves out something critical.
What we think it should mean
Real mastery is two things at once: accuracy AND fluency. A kid who can solve 7+8 correctly but takes 12 seconds every time has not mastered 7+8 — they've worked it out. Working it out is fine in the learning phase, but it doesn't free up cognitive bandwidth for the next thing (multi-digit addition, word problems, mental math). True mastery is automatic.
So in Rodybee, a skill is 'mastered' only when the kid hits both:
(1) accuracy at or above the threshold (typically ≥95% on recent attempts), and
(2) average time per exercise at or below a target (5 seconds for fast facts like single-digit addition, longer for things like geometry).
If only accuracy passes, the skill stays in 'practicing'. The kid keeps going. No shame, no panic — just more reps.
Why this matters in practice
Without the fluency floor, kids drift into a state where they 'know' the math but can't actually USE it. They get to multi-digit addition and stall, not because they don't know how to add — but because every step still requires conscious effort. The cognitive load runs them out of room.
Adding a fluency requirement adds maybe 1-2 weeks per skill. In return, you get a kid who, six months later, can do mental math while listening to a story. That trade is worth it every time.
What it isn't
Mastery is NOT a final exam score. We don't make a single big test the gatekeeper. We use continuous practice signals (the readiness thermometer) to decide when to confirm with a small block test. The block test is the cherry on top, not the cake.
Mastery is also NOT permanent without spiral review. A skill 'mastered' three months ago can quietly decay if it never reappears. That's why every Rodybee practice session mixes 80% of the current block with 20% pulled from previously mastered skills. The math has to keep coming back, or it leaves.
TL;DR
Mastery in Rodybee = accuracy AND fluency, kept alive by spiral review, confirmed by small block tests when the data says the kid is ready. Not a label. Not a checkbox. A working state that the system protects over time.