To which school was David sent? How did they treat boys in that school?

Young David is sent by his wicked stepfather, Mr. Murdstone, to school at Salem House. It's a grim-looking place in an advanced stage of decay. There are no boys there; they've all gone home for the holidays. David has been sent to the school early deliberately by Murdstone as a punishment.
When the boys return to school, David becomes an object of curiosity. As expected, they make fun of the new boy, dancing about him, patting him on the head like a dog, saying, "Lie down, Sir!," and calling him Towzer. But it's generally just mild joshing, and that's in no small part due to the generous, warm-hearted Tommy Traddles, who personally introduces David to as many boys as possible. David comes to form a close friendship with this thoroughly decent young chap, who, despite his unprepossessing appearance and chronic clumsiness, is one of life's good guys. The same cannot be said, however, of James Steerforth, who also becomes one of David's friends at Salem House.
In general, the boys are treated appallingly at school. The headmaster, Mr. Creakle, is a sadistic brute and bully who takes great delight in beating the boys at the drop of a hat. For some reason, he's got it into his head that David likes to bite people, and he singles him out for some especially brutal thrashings. Creakle's a close personal friend of Mr. Murdstone, which should surprise absolutely no one. Birds of a feather flock together, as the old saying goes.