When I was young, I went to a Montessori pre-school, but was moved to a public primary school as soon as I hit reception age.  I finally found out why:

"Livvy, I put you in mainstream school because when you were little, your idea of relaxation time was to go and get a workbook out of the cupboard and do that."

My mind flashes  to the puzzle book on my bedside table, and textbooks all over the desk, which I've been noting for the last 2 days, because I don't feel like playing video games.

"... Mum, I STILL do that."

Good to know that I've always been like this, and it isn't some defect in my upbringing or schooling that makes me an introvert. It's just who I am :)