2 children, aged 8. Child A is quite anxious and sensitive but is learning to stand up for herself. Child B likes to get things her own way and will run to teachers to tell tales. Child A will cover for Child B if questioned by teacher so that she does not get B into trouble.
Child A and B in friendship triangle with child C. Previous class teacher raised this as a concern as child A was often excluded but this has been dismissed by other class teachers.
Child B is now actively seeking to exclude A from playtime games with other children, and specifically Child C. Playground staff enable this by telling Child A it is her choice if she does not join in B's choice of game.
C is v friendly with A when it is just the 2 of them, but is swayed by Bs more dominant personality.
Of course A doesn't need to join in but it feels like B is manipulating the situation by preempting / instigating teacher intervention and getting her POV across first.
A's response is to go off by herself but this leads to questioning by teachers who reiterate it is her choice not to play.
I'm at my wits end. I've tried to encourage A to play with others, to stand up for herself, to distance from B and C.
When A has tried to build friendships with others, B steps in and asserts her friendship with other child.
B has physically hurt A outside school setting but under circs school unable to act.
What do I do next?