Do you punish her at home on the days that she acts up? Maybe a little punishment is needed to drive the point home that she has to behave at school or be "grounded/time out" at home. Restrict her from some of the activities that she likes when she acts up, but then give them back when on the days she behaves...
She needs to learn that there are consequences to acting up.
If you don't get this point across now, it will get worse as she gets older...
See if you can get her to talk about it. What is wrong at the new school that she doesn't behave? Is there a teacher or kid that she doesn't like?
Is she trying to manipulate you into taking her to another school because she doesn't like this one??