Earlier quoted context omitted.
> As soon as summer resets their brains, they suddenly have large gaps in knowledge that slow next year's learning. One loves to say that summer vacations are long so that pupils have time to fill the gaps for the next school year. If they don't use this time (or their parents don't urge them to), it is their problem.
Nobody's spending their vacation studying if they can avoid it.
If you have huge gaps in the subject matter of some subjects, you hardly cannot avoid it (and your parents will likely take care that you cannot avoid it ;-) ).