Judging from the way the horses are behaving, spring has well and truly arrived.
The spring has significant affects on not only the physiology of horses (changing coats) but has a huge effect on their behaviour.
Hormones are in high gear which can result in the kinds of behaviors that are not predictable or foreseesable, especially if your horse is new to you and this is the first spring you have owned/ridden him or her.
Remember that the grass is growing and nature is just doing her stuff and your horse is behaving just as nature dictates. He may be unpredictable and feel about to explode but stick with it, he just needs tactful riding and thoughtful riding until everything settles down. This is a good time to add more intricate patterns into your school work to keep him occupied and do not worry if accuracy of the school movements suffers, but continue to work on being calm and consistent yourself.
More important than normal is the ability to stay focused even when your horse doesn’t-this is not the time to lose your temper should he become very testing-it is not personal, and we should remember at all times to continue to work in a way that encourages trust.
Not easy-but essential!
Good luck, and just remember spring doesn’t last forever!