I wanted to like this show, and I may give it another chance, but my initial impression is the same as a previous poster: they are trying to hard. Every line doesn't have to be a joke; every episode theme doesn't need to be such an obvious trope.
Part of the problem is that since Corey is such a central part of the show, we who love BMW expect this to BE a true extension of BMW, and it's just not. The central character of the show is meant to be Riley, and she is adorable but I can't yet care about her to the extent that I do/did care about Corey. The other characters are mostly OK, although I think Lucas seems to be a talking Ken doll and Topanga is reduced to the Queen of Snark instead of the multilayered lady we knew her to be on BMW.
My two favorites are Maya and Farkle, although even they have, so far, seemed to be stereotypes. I see the actress who plays Maya is trying to bring individuality to the character, but she is (obviously) a female Sean. And Farkle, while adorable, seems to have adopted the persona of the missing Eric.
I haven't given up on this show yet, but if the episodes I watched are an example, I can't see it lasting too long. Young viewers who did not see BMW are not going to get why they are supposed to care about Riley and/or why Corey being a teacher is so significant.
Lastly, kudos to the posters above who pointed out that Corey needs to - at least briefly - interact with other teachers. And they DO need an authority figure in that school, because it is, so far, a model of "do your own thing and pretend to listen to/respect the teacher"