i honestly do not know how it worked becak in the early 1900's but wouldnt they still have had to go to school instead of playing on the moors everyday - what kind of life would that be for kids if they had nithing to do but play on the moors?
There was no mandated/required education at the time. There were public schools that you could send your children to, but a person of Mary/Lord Craven's social class would have hired a governess or have gone to a private boarding school (like Lord Craven mentions in the book/film. Mary makes the choice to stay at Misselthwaite instead of going away to school.
I don't think there was compulsory schooling back then. And even if there was, have you seen how isolated Misselthwaite Manor is? It would be impossible for Mary and Colin to attend day school. They'd have to be boarders. But at ten years old, they've probably missed the boat for that.
As you can plainly see, Mary, Master Colin and Lord Craven are all fabulously wealthy (You would have to be to keep a staff of servants like that). People who were this rich, often hired tutors or governesses to teach their children privately at home.
If you are referring to Dicken playing in the moors all day-he was poor and poor children of that time got very little if any education. As soon as they were old enough to work they went to work. As others stated -wealthy children had live in nannies who also taught them.
As for Collin- they didn't expect him to live and probably didn't bother with educating him.