Your parents reactions and discipline is quite common, sorry.

Before you read remember I am 29, deal with mental illness, my son's 10.5 currently. He participates in self harm multiple times a day for years, and has had (at least) two suicide attempts thus far.

Currently:
I don't do grounding like that. I will take away things until curtain things are done ie. Home work is not done in x amount of time (twice as long as it should take.) you get x taken away. If it's done on time the next day you get it back. As he gets older volunteering will be his main form of "grounding".

We homeschool but this was / is our plan if he ever chooses / has to enter public school.
As far as grades: If my sons grades were that bad I'd ask for a meeting with the teachers to find a solution. Ie. Stay after school w. teacher and do homework w. them. Mainly so the teacher's understand you are trying. I'd talk to him about why things are so crappy and take notes before the meeting and after so that he can agree with the terms too. He'd go to the Dr.'s making sure there's no physical, mental or learning issues outside his control that are effecting school. Yes this includes a drug test.

I'd probably have him tutor in an adult "learn to read" center or work with kids that really struggle with school. So he'd be volunteering after dinner & weekend for the semester. If he can find time to do other things great he can do them outside all his other obligations. I seriously doubt he'd find the time.

Disciplined to me is for taking the time out to figure out why things are important to us as parents and learn how to avoid getting in trouble again. I believe leaving a person with nothing to do is just begging them to cause trouble.

Now for the suicide attempt:

Remember my husband and I deal with our own mental illness so we're more understanding to it. It's so scary and painful to hear your child doesn't want to survive and tried to end his pain. Some times that comes out in anger and over reacting.

We've dealt with this a couple of times. We talk to him explain he's not bad, we understand and that it just means that his Mental illness is acting up. We talk about what he wants to do about it and what he needs from us. We come up with a plan. We ask if we can inform his dr. and therapist. Whatever he says we call his pdoc and therapist for emergency appointments. We do not inform them why if he says not to. We also look into better options to learn coping skills. ie. more therapy, sports, clubs. His voice weighs heavy in his treatment because at 18 he is fully responsible for his mental health.

As far as mental illness we understand that it's a life long obstacle that can effect every aspect of life including school. All we can do as parents is hope, be an example, teach him how/who to ask for help, teach healthy coping methods, apologize when we're out-of-line, keep lines of communication open, give him tons of outlets and a slew of options if he feels he can't talk to us. As his parents it's our job to advocate for him and teach him to successfully deal with his mental illness.