I went to an inner city public school for several years. The last year I attended (I was pulled out and homeschooled afterwards), one of my teachers made a cell out of bookshelves to put students who had misbehaved. They were all black. When called on it, she said she was 'getting them used to it.' There was also a lot of petty vandalism, bullying, and the educational quality was pretty miserable. If it makes you feel any better, I'm almost certain this experience was an outlying data point.