The first year in a new school, be it year 7 or 9, is hell. They all want to be cock of the walk and it takes until at least the end of the spring term till they settle down. Add to that no longer being top of his old school or at least used to it, new teachers and, groan, puberty, and you have a recipe for unhappiness and dramatics.
We found the following helpful but it hasn't cured the problem,
Boundaries
Earlyish bed times and enough sleep
Limited access to any thing electronic, tv, games, ipod etc
Plain 1950s style food ie mainly home made, yes pasta but not a pasta sauce, a home made one, to cut down on additives and junk,
Vitamin pills
Exercise
Having ways of dealing with the anger
Checking whether he was being bullied
Checking whether he was finding some subjects hard, ditto teachers,
Finding opportunities to talk with no eye contact, eg exercising the dog, doing the washing up, whilst on a journey,
And, never got this far, bit encouraging to write a journal
Seeing friends who are nothing to do with school at weekends etc
But I'm with MrsM, so would I and I think Ds would have been.