In equestrian terminology, a schoolmaster is a horse that has been trained to a high level in a specific discipline and is used specifically to teach a less experienced rider that same discipline. The schoolmaster's value is that it already knows the job: it carries the muscle memory, the conditioned responses, and the established way of going that allows a developing rider to feel the correct movements, responses, and timing that would otherwise take years to develop on an untrained horse.
Where the Term Is Used
The term is most common in dressage, where a horse trained to Prix St. Georges level or above can allow a lower-level rider to feel half-passes, flying changes, piaffe, and passage that would be impossible to ride on a horse that has not been trained to those movements. In show jumping, a schoolmaster is a horse with experience over difficult courses that allows a junior or developing rider to learn the approach, distances, and rhythm required at height. In eventing, a schoolmaster is a horse with cross-country mileage that allows a novice event rider to learn water, ditches, banks, and combination fences safely.
Characteristics of a Good Schoolmaster
A schoolmaster must combine high-level training with a patient, forgiving temperament. A horse trained to Grand Prix dressage that is tense, reactive, or punishing to rider error is not a schoolmaster, it is a difficult horse. The ideal schoolmaster accepts the aids of a novice rider calmly, performs the movements it knows in response to correct aids (teaching the rider what correct feels like), and tolerates the inevitable errors of a developing rider without escalating. Age is typically an asset: a horse in its late teens that has competed successfully at high level and whose competitive career is winding down is often the ideal schoolmaster, combining deep muscle memory with reduced reactivity.
Price
Schoolmasters command a premium: a Grand Prix dressage schoolmaster capable of teaching flying changes and piaffe may sell for $30,000 to $150,000 or more, despite being past competitive prime, because the teaching value is real and the supply of suitable horses is limited. For jumping, an experienced Preliminary or Intermediate event horse in its mid-teens may sell for $10,000 to $40,000 as a schoolmaster after its competitive career ends.
See also: green-broke (the beginning of the training spectrum); Thoroughbred (OTTB) for a common source of affordable schoolmasters in jumping and eventing.