I'm pro-suicide, but school may not be that big of a deal. I was found truant twice, sent to a charter school, later dropped out of college, found a menial job as tech support in a call center, and then rose up a bit to management over 9 years.
If you can just pass and manage to get a job, your grades maybe won't be a big deal. If you still aren't happy, there are plenty of ways to ctb.
Or you can order some cheap ways to ctb now and just see how far you are comfortable going. That's where I'm at right now. I have all my SN supplies now and it's a nice feeling to know I just need 48 hours of solitude, but not a nice feeling of leaving my family mourning.