Yes, you get full credit to your HS GPA. Whether or not it factors into your college depends on if you use the credits after high school (and if they transfer to where you're going). Usually, these classes are very weighted. I've gotten a 4.3 GPA for one trimester. On the other hand, don't forget that colleges put a lot more stock into your unweighted GPA than your weighted, so the only thing that weighted GPA's are really good for are pushing you up in class rank.