I read all Patricia Leitch’s Jinny/Shantih books in the 1980s, but I’d outgrown them by the time that the Kestrels series, of which this is the second, came out. This is along similar lines -pony book, lower middle class families rather than the upper class/upper middle class families usually found in pony books, slight touch of mysticism.
The two main characters actually rather annoyed me. One of them had a badly behaved dog which caused havoc everywhere. Think Bruno Maynard in the Chalet School books. There are few things which I dislike more than badly behaved dogs. The other one called her grandmother “Narg” because it was “Gran” spelt backwards. Why??! Why not just call her “Gran”?
However, as a short pony book for a child of primary school age, it’s quite entertaining – there’s a bit about learning to jump, as the title suggests, and some drama with feuds at the riding school, a charity pageant, a famous showjumper turning up and a horse being stolen. I won’t be bothering with the rest of the series, but, if I’d read this when I was 8 or 9, I’m sure I would have done.