I went to Catholic school from 1st grade through 6th grade. Not because I was Catholic (although my parents were, by the time they had me, they didn't have me baptized or had me do CCD or First Communion) but because it was the only English speaking school in Macau (near Hong Kong and China).
I have mostly fond memories of going to this school even though they were strict.
I remember in 1st grade, I didn't do my homework once so I got hit with the ruler on my hand 10 times. Then she (not a nun) said "I'll bet you'll remember to do it tomorrow night". I certainly did.
In 3rd grade that nun would give us homework for every single day of our vacations (which was sometimes two weeks long). She would yell at us for having long nails and tell us to have our mothers cut them. She'd send misbehaving kids into the classroom next to us with a sign on our chest stating what we did wrong (I never had to do that though, thankfully). They'd have to stand there for the rest of the period.
In 5th grade, I had another mean teacher who was not a nun. She made me stand and say something in Chinese and I didn't know how so she made me stand for the whole class period and was laughing and picking on me; one of her favorite sayings was: "Are you deaf, or dumb, or what?" She also stole my copy of the Declaration of Independence. I brought it in to show the class and she 'borrowed' it and would never return it and claimed she lost it. I think she didn't like me because I was American. I was the only American child every year.
I remember in 3rd grade getting cornered in the bathroom by 7th or 8th graders picking on me for being American; they were pushing me and teasing me. My mother had to come in and yell at the teacher of the girls' class and they never bothered me again.
I remember totally loving the daily Mass and longing to participate. I couldn't though because I was not officially Catholic. I remember in 3rd grade, right in the middle of class, the kids got to leave to go to Confession. I was jealous, again, and tried to go with them. A nun stopped me and asked me where I was going. I said Confession. She asked me if I was baptized and I said I don't know. She told me to go home and ask my mother. I did and was told I wasn't baptized. I was bummed.
I actually thought I'd be a nun when I grew up. I was so drawn to the Church even with some bad experiences. I lived near a big beautiful Church and would stand outside and listen and wished I could go inside.
I'll bet people from public schools have their share of horror stories as well. Times were different when we were young. My mother and father have their share of public school horror stories from the 40's and 50's.
Well, that's all I can remember now. Just wanted to share a variety of memories, not just horror stories.