Yeah, I use to get bullied from elementary school until the end of middle school. Honestly, the only thing that changed things for me was learning how to fight and standing up for myself afterward. Thing subsided more when I started defending myself but then I got tired of fighting dudes or getting jumped; ended up becoming cool with folks once they realized I wasn't dealing with there shit.
That came with a price though, I began to emulate the men in my community, they weren't the best role models and still to this day that's one aspect of my life I really regret.
Course if this is a professional connection you can't tell him to defend himself and start kicking everyone's ass. I'd probably just let him know that after high school is over he won't look back, he'll find others like him, he'll grow and experience so many different things, and he'll be proud of the person he is despite what people say now.
It would be better if you could give a personal example or have someone who serves as a model for all of that, but i would understand if you want to keep that boundary up.
If he's legit having suicidal ideation you should definitely get him to talk to a therapist.
