Horse opens her mouth, stretches her neck out then pulls her head down?

She's a young horse, and she hasn't accepted the bit yet. Perfectly normal. My mare has about the same amount of time under saddle- and she does the same now and again.

Keep the contact, and increase the pressure on the bit when she puts his head down. Release the pressure when she holds her head normally. Soon she will realise that there will be LESS pressure when she keeps his head and mouth quiet- and MORE pressure when she puts her head down to evade the bit. If you let her get away with evading the bit, the problem will get worse.

Get her teeth checked- and have a look at her mouth conformation. It's possible she's not comfortable in the french link, and needs a special bit.

I've got my mare in a pee-wee training bit, and will soon make the transition to a Myler comfort snaffle.

There can be many reason`s for this,

The most likely one is that she is still getting used to the bit and just testing it so just give her time.

The bit might just not be right for her so a happy mouth would be good but i would go for straight bar as some horses can`t stand linked or jointed.

Get her teeth done as it might be something simple as a sore tooth.

Try all these solutions and see what happens.

Why is she in such a strong bit even though she is so young? No youngster should be in anything but the mildest snaffle bit at least until she is fully schooled!

I really do despair. What do they teach you all in your riding schools these days?

All horses have different shaped jaws, thickness of tongue and lips, and their bridges (roof of the mouth) may be shallow or concave. If it is shallow, then she has no room to accommodate certain mouth pieces - it hits her in the top of her mouth. She is anticipating or even experiencing pain and discomfort.

Why were her teeth not done before you started riding her? You could have saved her a lot of pain and discomfort if you had thought to check her mouth to see what shape it was in BEFORE bitting.

She might also be experiencing tension in her back - and no wonder, she is probably too young to be ridden and has, of yet no muscle to bear weigh, so the head forward and down is a way of relieving that tension. She has a lot to put up with when she is starting out.

How long did you practice bitting her before someone swung a leg over?

Why wouldn't you have her teeth checked before even attempting to train at bitting?

What does your trainer say?