Can anyone help me.. I can't remember the name of a movie (I'm pretty sure it's from the 80's)?

I used to watch this movie as a kid and can't for the life of me
remember who's in it or what it's called.
This is all I remember:

The movie is about a teen girl and about her life at school (I think
it's a boarding school) and home.
Her father (or could be mother's boyfriend) is very mean to her and
her little brother
I remember a scene where the father is trying to cut the young
brother's hair and the little boy is freaking out
The girl finds an abandoned house and puts stencils all over the walls

There's a scene with the mom and the daughter where it's raining and
they have to catch the water with buckets
The teacher was really nice to the girl and concerned about her
The girl runs away at one point.

That's all I can remember. I also vaguely remember a scene with
swings and with the car.. running out of gas I think. And the father
(or step father) being really mean.

Sorry, I know that's not much to go on. I think also the family was
british. Or at least the mom and brother were.

Anyone have any idea what this movie is?