Join Date: Sep 2011
Location: Germany- but not German =D
I agree with upnover, he may have also learnt to pull his reins through your hands, and now evades the contact because you can't pull him back up, so to speak.
Firstly, however, as this is a horse in training, I would suggest getting his teeth checked, back checked, and saddle checked. He may be in discomfort, and pulling his head down and evading the contact is elevating the problem for him.
If you get these checked and its non of the above, it means somewhere your training has failed somewhere. You need to take him to more basics, more transitions, make them clean. You can't fight a horse's head and neck.
Make sure you aren't fixing your hands on the reins, and if he does drag you down, sit back, sit deep and sit tight, ask him to work more from the behind. My old horse used to do this, and he learnt if he did, he'd get a boot in the side, and within a week it was resolved.