Whenever I see Japanese school years translated to English, either in vocab lists or in manga/anime translations, it's always with reference to the US school system (i.e. n'th grade). As I'm not American, that makes no more sense to me than the original Japanese. How old are the children in a 小学校, a 中学校, a 高校 (and any other kinds of school I've missed), and how are the years named/numbered in each?
In short, if a schoolchild tells me they're in such-and-such a year of such-and-such school, what does that mean? (Or conversely, if I want to describe my school year in Japanese, which type of school do I say?)
Any other information that would help to describe the differences, such as which years have big exams, would be a useful part of the answer.