I would look at groom positions for eventers and jumpers rather than looking for working student positions. Look for ones who specifically need a groom who can ride as well, but also don’t be afraid to ask and say you are looking for the opportunity to ride/lesson. I did the working student thing but I got more attention, more varied rides, some money, and generally better living conditions as a groom than as a working student.
I will say working for a single rider is a way way way better life than working for a rider with a facility or for a yard. I worked for less money than a lot of grooms, but I did work for one rider, with only three or four horses at a time, and I got lessons. I then worked for more money and less everything else for a couple other riders. The first job was significantly more productive for me personally, and I would still be there today if my rider hadn’t basically run out of money.
You’ll find there’s a lot of…mobility as a groom. Like, some riders have the same groom for years and years and years, but a lot of them who go through grooms like Kleenex, for one reason or another. But there’s always another job, and there’s always something to learn. Even when I worked for a terrible awful girl, her coach was a well-regarded and successful Olympian, and I got to set fences with him, he instructed me on how he wanted the horses worked by me before she got on them each day, and I got the benefit of listening to him teach and watching him ride.