I'm going to state this as a rule of thumb:
If you can't get A's or B's average grades in high school then I don't think you should go to a 4 year college.
Note that I said A/B average grades. So if you get an occasional C or D then that shouldn't alone hold you back as long as you're averaging B's or better. I'm also applying this to a 4 year college. If you don't have the best grades then you might still consider starting at a community college or junior college either as a stepping stone to a 4 year school or to pursue a 2 year degree.
Why do I draw the line at a B average or better? Simply put I think that if you can't pull at least a B average in high school then you aren't going to be prepared to succeed in college. High school is easier than college and if you can't succeed academically in high school then you can't succeed academically in college. Going to college and struggling then dropping out won't really benefit you. Or if you go to college and work really hard and barely manage to get C's in college then it will be fairly hard to find good employment with such a transcript. Generally I think people in this situation are better off pursuing another career that wouldn't require a 4 year degree.
Why shouldn't people go? College is expensive and it has to provide a good return on your money to be worth the investment. If you can't succeed in college then it is wasted money. Too many people go to college nowadays and they are wasting a lot of money by doing so. Only 60% of people who go to college graduate within 6 years, so 40% of people are wasting money going to college.
So what if you don't have the best grades in school, then what should you do for a job? Tomorrow I'll list some career choices that don't require a 4 year degree.