My horse started rearing a little in the tie rack acting up around other horses what can I do to correct that behavior?

A horse that starts rearing at the tie rack is sending a clear message that something has changed — either in his environment, his management, his physical condition, or his understanding of what is expected of him — and the word started in your question is the most important word in it. Behavior that appears suddenly in a horse that was previously quiet deserves investigation before correction, because a horse that has been standing quietly at the tie rack for years and abruptly begins rearing is often a horse that is telling you something is wrong physically. Ulcers, hormonal changes in mares, back soreness, and neurological issues can all manifest as new anxiety and reactivity in a horse that was previously manageable. Rule those out first. If the veterinary check comes back clean, the next question is what changed in the management or environment around the time the behavior started. New horses in the barn, changes in feeding schedule, a new tie location where the horse feels trapped or exposed, increased workload, or even a single frightening experience at the tie rack that got missed can all trigger a pattern of anxiety that escalates if not addressed early. The tie rack itself matters more than most people realize. Evaluate where your horse is tied — is he facing a wall with horses moving behind him that he cannot see? Is he tied too short with no ability to move his head naturally? Is he tied too close to a horse that intimidates him? Sometimes the simplest fix is changing where and how the horse is tied before any behavioral work begins. For the behavior itself, spend time simply being present with the horse at the tie rack during low-pressure moments — grooming, hand-feeding, standing quietly while you do barn chores nearby. Build his confidence that being tied is a safe and comfortable experience. A patience pole or high-tie setup can be useful tools during retraining. Never leave a rearing horse unattended at the tie rack during the retraining period. The danger of a horse that goes over backward while tied is serious, and the panic that follows a fall while tied can set the training back dramatically and create a horse that is genuinely traumatized about being restrained.