How not to forget your school lessons during the holidays (15 min per week is enough)
Jul 2, 2026
You finished the year with a 14 average. You think to yourself "I've got this down." You go on vacation.
September arrives. You start classes again. And then: blank space.
You haven't forgotten everything, but 70% has become fuzzy. You find yourself having to relearn everything even though you had a solid foundation in June.
This is what is called Ebbinghaus's forgetting curve. And there is a hack to block it.
How much you actually forget during 2 months of vacation
The research is very clear:
After 24h without reviewing: you have already lost 30%
After 1 week: 60-70% is gone
After 1 month: about 15-20% remains
After 2 months of total slacking: there is less than 10% of the course left
There you go. Your whole year. Reduced to 10% of the content.
That's why teachers in September start with 2-3 weeks of "reviews". It's mathematical.
The good news: you can block the curve with very little
The beauty of it is that just one short review session is enough to reactivate your memory.
A short session (10-15 min) on a chapter already learned restores the memory trace to 80-90%. No need to relearn everything. Just to remind your brain that this info is important.
This is the principle of spaced repetition applied to the summer.
The minimalist plan: 15 min per week
This is the most chill version possible. For those who want zero serious studying during the holidays but don't want to forget everything.
One 15-minute session per week
You choose your time: Sunday evening, Monday morning, whatever.
For 15 minutes, you test yourself on a set of flashcards covering the essentials of the subjects you took this year.
That's it. Over 8 weeks of vacation: 2h of total work. And you come back in September with 70-80% of your year still in memory.
How to know what to test yourself on
Make a list of the 50 to 100 most important concepts of your year (all subjects combined). Turn them into flashcards.
An AI can do this in 30 seconds from your course notes. Otherwise, manually, you can do this in 1 hour at the end of June and it's settled for the summer.
The ultra-mobile format: the bedtime session
Do your 15-minute session in bed, before going to sleep.
Bonus: memorization during sleep. The brain consolidates information seen just before bedtime. It's the optimal time of day to engrave something.
The "I really want to be ready in September" version: 30 min per week
If you don't just want "not to forget" but also want to "be comfortable right from the start", add 15 minutes weekly.
Session 1 (15 min): review of past year's courses (flashcards, quiz) Session 2 (15 min): head start on the coming year (reading the first chapters of the syllabus)
Total: 30 min per week. Over 8 weeks: 4h.
You return in September with: your last year still in mind + a view of what's coming. That's the gap between the calm student and the student sweating from the very first week.
The 3 errors to avoid
1. Doing sessions that are too long, too far apart
"I'm going to do 4h at the end of the vacation to recover everything."
No. That doesn't work. 4 hours of cramming at the end of summer = 4 hours for nothing.
Better: 15 min every week all summer. Much more effective for long-term memory.
2. Rereading instead of testing yourself
If you open your notebook and read for 15 min, you've done nothing. You must test yourself: - Flashcards - Quizzes - Blank sheet of paper (what do you remember about chapter X?)
It's the effort of retrieval that wakes up memory, not passive reading.
3. Trying to cover everything
No need to retain everything. Focus on the 20% of concepts that cover 80% of the syllabus: the basics, the main theorems, key dates, essential vocabulary.
If you retain the foundations, the rest will come back quickly in September.
The ideal micro-format: 5 min per day
Even chiller than 15 min a week?
5 min a day of flashcards on your phone, like a casual app (Duolingo style). It's less time than a TikTok story.
You sit down with your phone, do 10-15 quick flashcards, and you're done.
Over 60 days of summer: 5 hours of distributed active review. No session ruins your vacation, and you return in September with 90% of your year in mind.
The "marked calendar" method
A productivity trick: mark "15 min review" on your calendar every Sunday evening. Check it off when it's done.
It's so short that you can't really get out of doing it. And the streak effect (a chain of successful days in a row) creates a mini-commitment that keeps you going.
Over 8 Sundays: 8 boxes checked. Your year is saved.
Why Koro AI is perfect for vacations
Reviewing during vacations, the number 1 barrier is friction.
Taking out the laptop to review on the beach = no way. Opening a binder = no way. Having to choose what to review = no way.
Koro AI removes these 3 frictions: - Mobile-first: you use the app like you use Insta - Everything is already ready: flashcards generated from your courses - The app tells you what to review: thanks to spaced repetition, it automatically brings back up what deserves to be reactivated
You take out your phone, do your 5 or 15-minute session, and put it away. No friction.
TL;DR
Without doing anything, you forget 90% of your year in 2 months. To block the forgetting curve, all it takes is 15 min per week (or 5 min per day) of active review on key concepts. You do this on your phone, from your bed or the beach, and you return in September with 80-90% of your year still in mind. It's not a question of time. It's a question of minimal consistency.