I agree, I think Belle is doing it herself so she doesn't have to go to school.
There's definitely something strange about the young boy but I dont think he has anything to do with it.
I'm not convinced she did do a good job on herself. The lady vicar was quick to point out that they hadn't took her straight to the hospital as her wounds were 'superficial'.
And to me, the mud/dirt on her arms and face looked overdone.
And then there is Midsomer Murders. Population of Midsomer Magna 380...cross that out, it's now 379, oops sorry delete that, 378, oh no another two, 376. Oh, someone's shot the parrot - and there's its owner, 375. They would warrant a major division of CID in their own right, if it was reality!