I ran across this figure and I believe it is true - about 50% of all geldings exhibit some residual stallion behavior even if there are no abnormal hormones present. So, your problem is not usual. The good news is you can train your gelding to correct his behavior.
You want to train the horse much the same way you would a stallion, which needs to know there is a time and place for everything and while he is being worked is not the time to have breeding on his mind. Many times all it takes is a stern voice command.
Those who show stallions often use the word "dress," reinforcing the word with a sharp jerk on the lead rope. I don't like jerking the leadrope, which can make the horse throw his head or back up. I usually just pop the horse under the belly with my hand and say, "dress."
Then, after the horse knows the consequence, if he starts to drop the handler can just say, "dress" and the horse is reminded.
Another method: Take your horse into a round pen or small paddock to groom him. Do not tie him. As soon as your gelding drops his penis, say "dress" in a sharp tone of voice. If he doesn't immediately dress then send him forward trotting laps around the pen. Use a longe whip or lariat to get him going forward in no uncertain terms. As soon as you see he is back to normal stop him and begin grooming again. If he draws his penis back up on the voice command then continue grooming. Repeat this routine until he stands and accepts the grooming and close contact without getting an erection or otherwise exhibiting stallion-like behavior. Your goal is for him to accept the grooming without dropping, and if he does drop you want to be able to remind him with the voice cue, "dress" when the kids are around.
Do this training when the children are not present, so its just you and the horse. But, depending on the age of children you are working with, I don't think it is a bad thing to explain why your horse is exhibiting the behavior and why you are correcting him - that he is acting like a stallion and when he does that he is not paying attention to his job, which is teaching them to ride and care for horses. Also, they need to know the difference between a gelding and a stallion. That a gelding has had surgery to prevent him from breeding a mare and fathering offspring.
I hope this helps solve your problem. I know how valuable those old school horses are, and I think you'll find it fairly easy to correct him with this method. These older horses are pretty smart and I think he'll catch on quickly.
Please let me know if I can be of further assistance.
Donna C. Smith
176 satisfied customers