Just want to confirm that the issue is school related. If not, you might get access through your child's GP more quickly, especially if you suspect something untoward causing the behaviour.
I don't mean to raise alarm bells unduly, but just thought this would be an appropriate and expeditious route to mental health professionals if the facts on the ground merit the approach. Sudden behaviour changes could be the result of a poor fit at school, or arise from any number of root causes. You know your child best.
In the meantime, you have my sincerest sympathy and best wishes.
