To me the teens have worn out there welcome.
You were very sweet to allow them the horsey fix and now they have taken advantage and pushed to far and to hard.
The horse is
yours and is
your responsibility to keep safe, sound and healthy...do not let the animal be pushed in riding directions he is not prepared for.
The word "No" if the teens not understand should now also be told to the parents so understanding is completely clear to all.
The teens abused your good nature and sharing so now they no longer have horse privileges of any sort with your animal anymore.
If you board, alert your barn to no more...
If you have the horse at home...lock the gates into the farm.
Lock the tack room and lock up the halter and lead ropes...
Place a few signs regarding trespassers beware....
After you make the phone call and speak to the parents, or go to the homes and speak in person to the parents...let them all know...trespass and you will be facing charges with the law.
your horses advocate and your own...no one else shall stand up to protect your rights or your animal but you...
Teens do not
intimidate me...very few things actually do!
Those teens ruined the chance to enjoy what was offered by you....to bad for them.
That's my take on it...they blew-it.
Now protect what they desire cause for some no is not graciously understood and becomes a reason to retaliate against...