Should I quit school? My gpa sucks and I'm depressed.

No. Education is one of the most important gifts you can give yourself. You deserve this gift. So your gpa is not high, just means you need to apply more effort or get some help. The depression is a second issue and you should get help with this. Your health is another gift, protect it, seek help, maybe talking with a therapist can help you, maybe some medication will be required. But seek help.
NO. Get treatment for your depression and then see what happens with school. Also consider other things like maybe adhd. Hard to tell without more information and how your grades were before etc. Contact your primary care physician as soon as you can to discuss the problems.
No. You should not give up just because of your poor grades. If you are depressed, seek help as it may help your grades of you treat your depression with professional help. You can also seek counseling to help you figure out what to do about your grades. If you have clinical depression then you should ask the school to allow you extra help because of your illness. They are legally required to help you.