What GPA do you need to attend good colleges?
Often people ask what GPA they need to get into such and such school. It all depends on the school. More prestigous schools want higher achieving students, so they set the bar higher. Others set a lower bar. My suggestion to you is to just try very hard and keep those grades up. You want as high as you can. A 4.0 would be good if you could get it. (Not everyone can). Most people say a 3.5 would be pretty good and could get you into a good one if you had some extracurriculars.
This depends on the type of college you wish to attend. Community Colleges will admit almost anyone who can afford to pay and pass the entry exam. If you wish to get into a more prestigious school, you should aim for at least a 3.0 GPA (B average) or higher. Highly prestigious schools will require you to have near a 4.0 GPA or extremely good SAT / ACT scores.