grading scales vary from school to school, and generally (depends) tier to tier. If you're just looking for a simple answer, to "what are 'good grades?'" class rank is where you should look. Top 5% at a T1 is awesome, just as Top 5% at a T4 is awesome. However, Top 75% at a T14 may be good, whereas Top 75% at T4 is not so good. Across the board, gpa's are not descriptive enough.