The heritage-language gap
Japanese-American children in Tokyo often have weaker English literacy than their US peers despite being native speakers conversationally. The Saturday school had been working the speaking + listening pillars well; reading and writing lagged.
Why Koydo's reader + writing tools fit
The Koydo Reader's CEFR-graded stories with audio + per-paragraph vocabulary scaffolding gave students a structured way to build reading stamina. The homework grading tool let tutors return marked-up essays with specific feedback — the missing piece in the Saturday school's previous setup.
Why the gap closed so fast
The students already had the spoken language; what they needed was the alignment between their conversational competence and written English. Once the reading + writing scaffolding caught up, the underlying linguistic competence carried them quickly.
What the school adjusted
Saturday-only cadence isn't enough for sustained literacy growth. The Saturday school added a 20-minute Koydo Reader homework assignment for each weekday — about an hour total per week, parent-supervised. That weekday consistency, more than the Saturday lessons themselves, drove the grade-level jump.