Meh! School schmool!!
I know a couple of people who didn't enter into formal education until they were over 10 and they went on to acheive university degrees (one of them was my mother who moved around a lot because of WW2). So my life experience tells me that people can be well adjusted and well educated without the benefit of primary school.
As for high school - I posted an article above about a student from a school that isn't even in the top 100 for HSC achievements who attained amazing grades.
I figure that attitude of the student is more important than the school they attend.

TBH I often feel that the education system these days is more about training our children than educating them. In order to qualify as a school they all have to agree to teach the state syllabus.