J.L.
Ah. My daughter, sweet, loving, turned four and it seemed like that day she regressed to a two-year-old. For her, it was a two month phase, misbehavior directed at me. I really wonder about some sort of regression at this age. She, too, went to the same school for three years prior, but with this milestone, maybe there is some anxiety about growing up, more expectation,etc.
We talked about how our days were going and if she behaved like x then y would happen. She's a smarty, so we talked like this at a calm time and I would follow through every time so she was able to predict the consequences. I gave her a ton of attention when she was feeling loving and set firm boundaries when, well, not.
Keep the consistency, as you are. Give us an update if things progress or change.