It's considered somehow disrespectful, but aside of a teacher it has no meaning.
I've checked in Doroszewski's dictionary and what i found:
1) pot. pog. nauczyciel, bakałarz - so colloquially, pejoratively teacher
2) pomocnik mełameda w chederze (nm. Behelfer) - assistant of Melamed in Cheder
This second thing requires some explanation. Mełamed is a teacher in Cheder (a type of Jewish religious school).
As the Jewish culture nearly vanished from Poland, nowadays nearly no knows this context and no one know why this word is considered pejorative.