I suspect your teacher wouldn’t have said the same thing about Lewis Carroll’s poetry, which just shows she was wrong — if “Jabberwocky” is a real poem with all its nonsense words, then Shel’s poetry is just as real. It’s like people being snotty about genre fiction not being “real” literature. Back in the day, a lot of what we consider “classic” literature was considered trash and junk. Especially things like gothic fiction and regency romances. Things that were considered diversions and entertainment for women. An English teacher should’ve known better.