We ALL felt the same way but you've gone too far to quit now. Yes, it seems like what you're learning is BS but, as mentioned above, it's not so much what you're learning as it is learning how to do research and figure out the solution to problems. Yes, calculators are great but if you don't know the formula to figure the square footage of an area, the calculator isn't going to help.
Say, you've saved up enough money to build your own garage to start your own shop and want to build it yourself to save money. You need to know how to figure not only square footage but cubic area to tell the concrete company how much concrete you need. Yeah, you could tell them the dimensions and let them figure it out but, owning your own business, you need to make sure they're not screwing you by over charging you. You might be able to slide by in life by ignoring social studies and history etc but you WILL need math through out your life.
And, as a business owner, speaking proper english (or French) and using proper grammer in your writing will go a long way in gaining the confidence of perspective customers and peers a like.
Like a couple others have said, body work and or automotive mechanical work is physically hard work. I know a lot of 40 year old body men who's knees are shot. They hobble around like 65 year olds. Not to mention the breathing problems they have from the chemicals and bondo dust they've inhaled over the years. Google "body work" or find a body working forum and search the posts for injuries. You'll find tons of guys talking about their job related health problems.
Here are a couple other sources.
http://annhyg.oxfordjournals.org/cgi/content/abstract/28/1/19http://www.lni.wa.gov/ClaimsIns/Insurance/Reduce/Prevent/RatesWatch/AutoBodyRepair/3412ClaimsByInjuryType.aspHere's a good source. Scroll down and read "Training, Other Qualifications, and Advancement" section. It states that "Courses in electronics, physics, chemistry, English, computers, and mathematics provide a good background for a career as an automotive body repairer." The article goes on to talk about saleries as well.
http://www.bls.gov/oco/ocos180.htmJust remember that even if you only just scrape by and graduate with c's and d's, you will still have a High School Diploma. I'm pretty sure the only time people look into your high school grade point average and attendance is when applying to colleges. I think employers just look to see if you have a diploma or not.
You're not really getting a jump on anyone by dropping out starting your adult career early. In fact, not having a diploma may put you behind those that graduate a year later with a diploma. Chill out and enjoy hanging out in high school with your friends for another year or so.
Good luck with what ever you choose.