jokes are a good start! it's hard to flirt with teachers because you cant like playfully take their stuff, or make fun of them cause well, they're teachers. try to become their favorite. do stuff they like, like for example, say you know this teacher likes typed papers but doesn't make people type, type the paper because it shows them you care. this is all i'v got, this advice might not even be right because, to be honest, i'm still trying to flirt with my crush. good luck!๐
