I had crummy grades in high school too. I think at that age I just didn't think about grades much as long as I was passing. I think my total gps was about 2.1 or so. That was 12 years ago give or take a year. Now I'm in my final semester for an associates and my college gpa is sitting at about 3.8 or 3.9. It should end up around 3.95 after this semester is over. I think it basically just shows that you're serious about your future if you finish a college degree with excellent grades. In the job world, it seems that college basically overwrites your highschool transgressions. Assuming you do well in college that is 
I wouldn't worry about the high school grades unless you have some kind of seriously deviant past.
By three methods we may learn wisdom:
First, by reflection, which is noblest;
Second, by imitation, which is easiest;
and third by experience, which is the bitterest.
'Confucius'