Firstly, welcome to the forums. Tough topic to give advice on as everyone reacts differently depending on the advice, are they open and talking to you about it currently? I would suggest reading the supporting someone with a mental illness section on these forums, simply go to the top of the page, where it says "The facts" scroll down to where it says supporting someone and have a read of that section. Is there maybe a school counsellor they can talk to as well?
My best for you,
Bullying can vary so much, however it should never happen, because all it does is make you feel as though you're not wanted, and when this happens causes depression, this will affect your home life and can stop any social life.
I hope you will come back and talk with us. Geoff.
Welcome to the forums and thanks for your post.
Sorry I just wanted to clarify - are you a teenager looking for some help, or are you an adult looking for help for a teenager?
Feel free to check this link out as it might help. There's a few different strategies here - https://bullyingnoway.gov.au/YourRole/ForTeens/Pages/Im-being-bullied.aspx