I had noticed that when the kids return after the summer break they go to school all guns blazing, then almost going towards the xmas break they become tired, run down,mine becomes weepy and naughty. A lot of the parents have said the same, they are in need of a good break, after all they are still little. If she doesn't perk up after the xmas break have her checked out. You mentioned her waking up bright as a button, it does indicate that she is in need of some rest and after that she feels ok again. Mine were always fine again and in the rest period they also had a growth spurt. When my daughter comes home from school now she has a little napnap as she calls it and she is 7.