This topic has more than 1 way to address it. Just as so many of our riding issues do. I will try to break this out into several potential reasons based on the most common first.
The high-headed horse
There are two main reasons a horse will ride with its head above its connection point or above level. What is considered “high” is dependent upon the horse’s conformation and muscling.
The first reason for a horse’s head to be elevated is a lack of drive. This is your horse that isn’t moving at a fast speed or being overly pushy. Yet its head is hard to get down. It feels like you have nothing in your heads and every time you try to pull on the face to get it to lower, the horse just sucks back more in its speed and possibly elevates higher or doesn’t respond at all.
This horse is lacking drive. Mechanically his head is sitting on the front legs which attach at the bottom of the neck. The muscles involved with the front legs are the neck muscles called the brachial muscles. So when the horse is using less of his hindquarters to push and instead is using more of the front legs to pull, it uses more flexing power in the neck muscles as a result. In order to get these neck muscles to release so the head can lower, you must activate more drive with your leg. Once the hindquarters push more than the front legs pull, you’ll see these neck muscles soften and the neck will lower resulting in the head dropping willingly.