Not too sure what country you're in... but ..... in the UK, I would suggest you make an appt with the school.... ask them to get assessments done on your child etc, ask for their opinion. Then I would make an appt to see your GP....talk to him or her.... explain what it is like and ask for help.... and keep on asking...
Do you have any friends who could give you a break?
What is yr 9 yo doing? Is there an underlying cause for the behaviour? How old are the twins? Are social services involved? If it is awful, you might be able to get some respite care????

Good luck.....

How long has this been going on? Are you a single parent as you mention you have no family around you?
Have you tried ignoring this bad behaviour and rewarding the good behaviour,it maybe a cry for your attention.
Don't feel alone, I had this from my 7 yr old daughter, but she was diagnosed with Autism. Have the school commented on this behaviour at all, because you never know your child may have something wrong.

Hi Johanne

Thanks for your message and really sorry things feel so bad - really think you need to seek local professional help - start with your doctor or GP

Kind regards

Dr Andy Gill