We call someone as a straight-A student when she or he gets only A’s on their exams; they always get good grades.
Juliar always studies hard. She’s a straight-A student in her class.
Being a straight-A student takes a lot of hard work and determination, but that doesn’t mean you have to give up your social life. If you get good grades, you’re that much closer to a good college which will lead you to a good job.