It's always difficult to keep up with slang students use because we aren't in their "world." But it always helps to at least have a general knowledge of what's going on in their culture. Here are two sites that list some common terms teens and pre-teens may use. In no way is it an exhaustive list, but I've heard several of them used by our students lately.
Also, if you ever have a question about what a word means or the actual definition behind it, Urban Dictionary is a helpful resource. It's very blunt and contains adult language, but it helps define some slang terms our students use.
Discussion questions with MS students: Do you use any of these words? Do they mean (insert definition)? What are some other words kids seem to use a lot and what do they mean? It's also a good time to talk about phrases you may have seen/heard, but may not understand...such as "Netflix and Chill."