You could go back to court and ask for these contacts to be supervised, if they've already said no contact at all they should agree to that with no problem and if the school have noticed the problems then ask them to make a statement to support your request.
I Have 3 children, oldest is 6 yrs old, there father walked out on them just over 3 yrs ago.
They use to have contact every second weekend at first, then I noticed the behaviour pattern would change for atleast 3 days after, so I put a stop to contact until my children are old enough to cope with the situation.
To be honest it has done them the world of good, But they don't actually ask about there real dad.