I have never even heard of Blyton and Streatfeild
Enid Blyton #1 Children's author (for maybe 30 years, UK and Ireland?) Teachers and Librarians were suspicious of her and some wouldn't stock her.
(Capt. W.E. Johns of Biggles fame, and not actually a Captain was #2 for many years)
Noel Streatfeild is EXTREMELY famous for the shoe books, so much that even though an English Author she is mentioned in an important scene in film "You've got Mail". I've 11 of her books (for research purposes, we sadly didn't have them when kids growing up.), the less known Gemma books were more useful for my research for the "Talent Universe" series, which is vaguely hard SF with some Psi powers chucked (there is a special school, so I read loads of Ballet books and School story books dating back to 19th C. Enid Blyton didn't write that many school books compared to earlier authors such as Angela Brazil and Elinor M. Brent-Dyer, there are about 61 Chalet School books and an unknown number of shorts published in comics and magazines. Angela Brazil didn't really write series, hence perhaps why less popular, but they are probably the best.).
Enid Blyton's two sets of School stories obviously inspired by the earlier authors.
J.K. Rowling certainly must have been seriously influenced by Enid Blyton. Not sure how much by the
Jill Murphy Worst Witch Series, but if not an amazing co-incidence.
Anne Digby "Trebizon" series must have been almost the last major School Series.
The fourteen novels were published between 1978 and 1994. Like Enid Blyton's much earlier creation, Malory Towers, Trebizon is located in Cornwall.
The novels follow the protagonist Rebecca Mason from when she joins the school in the second form through to the end of her fifth year. A major theme throughout the series is Rebecca's burgeoning talent for tennis. Other major characters include Rebecca's two best friends, Tish Anderson and Susan Murdoch, and her boyfriend Robbie Anderson.
Despite their more recent publication dates, the later books in the series are substantially harder to obtain than the earlier ones. This may be because fewer copies were printed during the 1990s recession in the UK book trade. The series is currently out of print but retains a dedicated fan base and titles frequently change hands in a thriving second hand market.
Some of the rarer books in the series are currently being reprinted by Fidra Books. All fourteen books are currently available on Amazon Kindle.
https://en.wikipedia.org/wiki/Trebizon
I have eight original paperback got at 50c each in a charity shop
There are a few US stories ALMOST like the British style, and maybe one German. But the style of boarding school in UK and Ireland in 20th C (some still survive) that the School stories mostly depend on seems unknown elsewhere. I'm not talking about Public Schools, but sort of Boarding Grammar schools that better off Middle Class parents sent kids to. By 1960s many were day schools only. In Ireland some connected to Protestant denominations, Convents and Monasteries survive.