I wouldn't admit either of those things, actually. Both are possible but neither certain and could also be false.

Perhaps the healthy, well functioning adults would have been so regardless of schooling. Perhaps the weirdos would have been so regardless of schooling. Perhaps schooling makes the difference for a proportion less than 100% of the students? How much less? Under what circumstances? Who could know with any confidence?

I honestly don't know how you could get clear evidence to say one way or the other as to schooling contribution to the causation of "weirdo-ness"

A school system produces the people who go through it. How much impact the school system had on them is obviously unclear. Whether they came out of it, however, is unambiguous. Therefore, since it is true that the school systems have produced at least one person of these types, it is also true that they can do so.