Unsurprising. If you have nothing else to do with yourself, marriage is kind of the natural thing to look toward. (Besides, for poor families, it reduces the number of mouths you have to feed, though school doesn't make that cheaper, so it isn't the primary cause.) School occupies your time and produces a rationale for not marrying.

In the West, education and then career advancement (and perhaps a pointless desire to "play the field") are reasons for postponing marriage...which has only produced demographic decline. (We ought to recognize human biology and take that as an immutable given, and then structure social practices around it instead of willfully engaging in Procrustean hacks and customs. This would counter demographic decline, because the fix is in essence simple: start having children at a younger age. Everything else should be built around this.)