He looks to be back at the knee. Hard to say in this photo. But.. consider this, a horse that would rate 100% conformationally correct, would not be useable.
And for those who immediately wish to disagree, then explain why Halter horses, whom are soo pretty to look at, are not used for hard competions.
He looks to be a cute nice horse. Some groceries and muscles and he could be really nice. Also, I do have to comment, whats with the tiny buckets on the fence, I do hope you have a larger water trough !