Get by in class
Six set phrases for the classroom: ask how a word is read or what it means, say you don't understand, ask for a repeat, say you have a question, and check your answer.
JLPTN5
わかりません／もう いちど いいですかwakarimasen / mō ichido ii desu ka
You say these whole, as they are: なんと よみますか (how is it read?), どういう いみですか (what does it mean?), わかりません (I don't understand), もう いちど いいですか (once more, please?), しつもんが あります (I have a question) and これで いいですか (is this right?). They are all in the polite form, because you say them to a teacher. Put すみません or the teacher's name in front, and they are polite enough for any class.