@moopet@bookstodon YES this one!!! It's awesome – and it took me a Very Long Time figuring out as an adult what that book was I could not forget.
Fun story: there are several really impressive books I read as a young person, not being able to remember name or author.
Only last year I tracked another one of them down. I saw a book cover in a used book store, thinking: could this really be...? And it was. Imagine my surprise realizing it was ALSO by Monica Hughes!! (Ring-Rise, Ring-Set). :D