I've got an offer from college development team to make a school website with them.
I've no idea of web dev except HTML, CSS, basic js and PHP.
Should I get in?

Yeah get in. You could learn from them, if they're good.

yes, those are the big four that you want to because a stronger developer

Ofcourse. Later in future you will have stupid coding memory and one thing to laugh at your self.

Seriously, when I look my old codes 4 years i am like woah so stupid I am.
So do I sometimes. But i learn from it.

Watch tutorials and take advices.