Generally, a high school transcript needs 24 credits. Some localities may have different requirements. If in doubt, check with the board of education in your area, or call a college in your area and ask how many credits they expect on a transcript. 
If your student is a high achiever, they may exceed 24 credits. This is fine, but try to keep the total number of credits below 28. Anything higher than that can look suspicious to colleges who are used to seeing standardized credit totals from public high schools.
If you have more than 28 credits, consider combining or cutting out classes. For example, you can combine separate physical activities (like ballet and sports) into a 1 credit "PE" course for each year of high school.
If your student has enough credits in the correct subjects to graduate per your state's requirements, they shouldn't have any trouble getting into college. It's not necessarily going to benefit them to have a huge amount of credits on the transcript. Variety is more important than quantity.