Juvenile fantasy
In
juvenile fantasy, protagonists are usually children or teens who have unique abilities, gifts, possessions or even allies that allow them to face powerful adversaries.
Harry Potter is the powerful young wizard, some of the children of the Dark is Rising series are immature Old Ones with magical abilities and in
His Dark Materials series they have magical items and animal allies. And children are actually the only ones that can enter Narnia.
This fantasy subtype seems to be typically British favorite.
Some juvenile fantasy series: