DS9 is not part of the Federation - there's no proper education available there, beyond what charity work Keiko O'Brien does, without much training or authorization.
Have we ever seen what the education systems in the actual UFP are like? We haven't even seen a Starfleet Academy lecture, even though we know lectures are still part of the SFA teaching method. We have only seen various exercises and simulations and tests.
Apart from that, we have seen a shipboard kindergarten, and that's basically it.
Moreover, there's no dialogue on future education methods - no downloading-knowledge-to-brain-through-machinery, no sleep-learning, no advanced teaching methods, nothing. Perhaps it has simply been decided that organized education is inefficient and ultimately superfluous, and everybody is free to learn at his or her own pace?
Indeed, in TNG "When the Bough Breaks", a preteen struggles with calculus, while in DS9, Jake Sisko, very much a teenager, is "still" doing algebra. In a unified education system, it would be basically impossible to teach calculus first and algebra afterwards.
...Unless future educators have found out that the human mind learns calculus easily before the age of, say, eleven, and then shuts down, much like we today know that languages are best acquired at an extremely early age.
Timo Saloniemi