Me too, not just at school. My dad was an irrational alcoholic while I was growing up. I was always being told how I 'needed' to live up to the standards of my much smarter older sister. (Quite funny when I think that in the late 1980s we both did MENSA tests and my IQ was measured 20 points higher than hers at 148).
I'm now 52 and have no self esteem. No real friends as I got in the habit of holding people at arms length and have never managed to break that. Very shy but in trying to act not shy I've come over as abrupt and false.