While I'll take an FEI horse in a New York minute, young horses are frequently more in my bracket and there's something pleasurable about creating something from barely broke. Young horses also present the alluring thought of potential, and really show the transformative effect of training. So watching and working with them, for me, provides the most entertainment.
I'm also lucky that I have good owners and breeders who provide and trust me with their kids.
My oldest youngster, Danzador, is a five year old, and my youngest, Flair, is a four year old. However, where Flair is on hiatus, Danzador is being actively ridden and worked (sorry buddy, no maternity leave for you).
Danzador is a wonderful athlete. He's mastered a lot of concepts at an early age, where several professionals have complemented him on not only his basics, but his promise in the upper level work. At five, he already shows a more confirmed piaffe than a lot of Grand Prix horses showing today. Mentally, he's sharp and handles pressure exceptionally well. He's at a point in his development where he's very much set to go forward and shine in his career, especially start making steps to becoming an FEI horse.
Physically, he's catching up to the warmbloods- PRE's are notoriously slow to mature- and like all athletic young babies, somedays you are brilliant and par for course and other days you can't turn left to save your life.
Thus go the way of babies. No one said it wouldn't be interesting.
There's a lot of varying opinions on what a young horse should do and how fast they should progress. Everyone's program and horses are an individuals in that regard. Ultimately, my end goal with my horses is that I have an sound, happy athlete who is capable of going and doing the FEI levels.
In my book, the young horse years (three to seven year olds) are critical for putting the basics on some of the larger concepts.
Yes, they should forwardly walk/trot/canter on the bit and stretch to the connection, they should hack (preferably on a loose rein without killing you), they should tie and stand; they should mind their manners, and go places and not be total embarrassments.
They should be good citizens first, and athletes second. Simply because having a half-ton animal on top of you is not only rude, but dangerous. Respect is a universal concept.
But they should also know lateral work, they should be building strength to carry by learning to collect and extend the paces. They should be adjustable in the outline and learn extend their balance points. They should be playing with half steps, doing simple and flying changes. They should go in a variety of bits and bridle combinations as they progress.
In short you need to have expectations. Which when it comes to young horses, can be an unpopular thought.
They should, and deserve, to have a preview of the regular questions that are coming down the pike to help develop their physique and mental capacity to handle pressure. It's easy to become trapped in the time warp of Junior being five forever (seriously, I still think Sinari is 10), and perfecting the lower levels before moving on instead of creating a solid foundation of basics instead. It's not easy to get them out of their comfort zone because you're bound to get a reaction.
It shouldn't be perfect. It should be correct.
In a dressage horse's (and most sport horses') career, they'll actively face these questions time and time again, at each level with greater volume and intensity. It takes uninterrupted years of carefully building strength, balance and coordination up. In short, a horse will not magically be an upper level anything with a wish, a wink and a nod. You have to create and foster them through this by being consistent, and systematic.
It doesn't mean hammer on your five year old to do the entire Grand Prix piaffe/passage tour, or shove your three year old into a second level balance for 45 minutes or have your four year old do tempi's. It doesn't mean immediately take the horse who was back and broke 30 days ago and jump around a course of 3'0 questions, also doesn't mean go out and do it everyday until everyone is burned out, either.
It means this: school them in moderation but with the expectation that they go on, and have the capacity, physically and mentally to handle the work that lays ahead. Develop their toolbox. Support them with a good network of nutrition, farrier, vet, equipment and body work so they can do their jobs happily. Above all: use common sense and be aware.