Loads of those listed here:
Arthur Ransome (my favourites of which are Swallowdale, Pigeon Post, and The Picts and the Martyrs)
Antonia Forest (I only knew about the school ones as a child)
Enid Blyton (initially The Five Find-Outers, then the Adventure ones, then the school ones) - my mum had to limit me to one Rnid Blyton per library visit or I’d have read nothing else
Susan Cooper (The Dark is Rising is my favourite)
The Rebels of Journey’s End (Australian, I think, and by a child author)
Anne Fine (A Pack of Liars, Crummy Mummy and Me, etc.)
The Demon Headmaster - Gillian Cross
C.S. Lewis (I like most of Narnia, but especially The Voyage of the Dawn Treader)
All the Green Knowe series
Redwall and sequels (Mossflower, Mattimeo etc.) by Brian Jacques
Charlotte Sometimes
Goodnight Mister Tom (I found the film version disappointingly mawkish)
I’ve always preferred naturalistic stuff to fantasy, but to be honest as a child I read pretty much anything.