does summer school gpa replace regular gpa completely? Does it affect you college application?
That depends on your school.
In my school, a summer school grade maxes out at 65, regardless of how you actually do on the makeup final exam.
As far as I know, colleges don’t accept the grade (or gpa), they only accept the credits for that course. So if you got an A+ in Astronomy, a C+ in Chemistry, and a D- in Digital Theory you will only get the credits for Astronomy and Chemistry and you will have to do Digital Theory over again.
It’s a pass or fail type of thing, you get no grade for it. The grade they gave you for the class is only for that particular school you took the course in, not for the college that you plan to transfer those credits to.
[note] Keep in mind, the college you are applying to may have standards as to which colleges they will accept credits from. Each college has a list of other colleges in a database and the list of classes for those colleges for which they will accept credits from. This is an important note to be wary of because a Calculus 2 from a community college may have to be taken WITH Calculus 3 in order to be accepted by your future college for just Calculus 2 alone.
I’m under the impression that the OP was talking about high school summer school classes, to make up a failure during the school year.
Is that correct?