I also answered "I don't know," but the real answer is "I don't know the truth." What I know about my N mom's childhood was pieced together by things I heard from other family members.
M herself painted a picture of having a perfect childhood. She told me that she was an honor student, got straight As, and was sent to a special high school in London for gifted children (home was Canada). She was also a gifted ballet dancer, and had to go to London because the Royal Ballet was interested in her, yada yada. She told me that she had been accepted into a top university, but the family was poor, and could only afford to send the eldest child to college.
About 20 years ago, I went to a family reunion back in Canada and saw Aunts and Uncles who I had not seen since I left Canada at age eight. One of my aunts (M's sister), had a few too many beers and started telling me that my mother was extremely disturbed as a child, and that her siblings had to lock their drawers because she stole from them. Same aunt also told me that M was such a problem, that she had to be "sent away" when she was in HS.
I've also felt (just my own gut feeling) that M was bullied in HS. When I became a teen, M was insanely jealous of me if I had friends, was asked on a date, made the tennis team, etc. So much so, that she went to great lengths to sabotage my dates by humiliating me in front of them, so the news would get back to school, and I ended up being bullied myself.
So I'm just drawing my own conclusions based on a giant puzzle that I've pieced together over the years. M has the IQ of a fifth grader, so I don't believe any of the honor student stuff. More likely, the "school for gifted children" was a boarding school for troubled kids. So even though I have a gut feeling about it, I'll never know the whole truth, so it will always be speculation.