Is it possible to attend my "backup" school but reapply to my top choice and go there if accepted?
Common scenario: a professor is recruited to go work at a different university; s/he takes his or her students along.  No one bats an eyelash.

The quicker you can make the change the better; you need not feel at all guilty.  It's just not a good fit.  Your current school would be a great fit for someone who wants to teach.  But it's not a good fit for you.