I agree with Fulford15. See-sawing is not acceptable, neither is it correct. It doesn't encourage connection over the back, or do anything besides create a false head-set. Many people are happy as long as their horse's head is down, because they think that's all dressage is. Usually it's beginners who do this...people who haven't had the education necessary to realize this is not correct.
If my horse's head is getting to high, I probably would ask him to move with more energy while using small motions with my inside rein, asking him to flex to the inside and releasing when he does. (depending on situation) And if I was having a consistent problem with this, then I would go back to basics with him, because obviously his back is not engaged.
So yeah all in all, it's a no from me.
DRESSAGE, n.: the passionate pursuit of perfection by the obsessively imperfect -Author Unknown