Sounds really awful, and worryingly unsafe.
How close by do they live, slim?
I agree about talking to the school - if the statutory services can't intervene on your say-so, then the school might alert them.
It's difficult. It would be hard to prove actual neglect, even with all the details in your post, but it's very poor parenting 
AI is here - Barclays is cutting 5,000 jobs
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Wes Streeting announces we have 1,000 days to prepare for war.
