Do you know how I can get a list of the most common expressions used in British classes...(The way Ss get permission to get out, talk about their courses, refer eachother,...etc. Thanks!
There are some articles here on classroom language here: Articles for English Language Teachers - UsingEnglish.com
However, are you asking about schools, universities, language schools or what? There will be diferences depending on the type of institute, like calling a school teacher sir/miss, a form of address that isn't used at universities.