Educate your students on the symptoms of common ailments; colic, laminitis, shipping fever, rain rot, ring worm, etc.
Teach them about correct horse management practices; routine vet work, teeth, vaccines, farrier.
Talk about body clipping styles and techniques, talk about blankets used, weights uses and applications.
Educate them about braiding, styles, techniques, etc.
Educate them on shoeing types and styles
Talk about 'reading' horses' body language. Eager, frightened, attentive, agressive, etc. Talk about ear position, muzzle and neck position. You can draw diagrams or research expressions on various websites.
Educate them on the horse's reproductive and digestive tract. If your students show, educate them on what's legal and illegal; ie: drugs and procedures that will disqualify someone from showing in their chosen discipline.
Describe the different riding disciplines out there. Talk about different bits and their application & effect on horse' mouths. Talk about different saddles and how they effect rider position & sport.
Talk about pasture maintenance, fencing styles & preferences, shelters, bedding differences & preferences
The list is endless...