PARIS: Why are they letting all these extra people in? They just take up space and screw up the curve.
Some schools grade on a curve, meaning that the performance of the group overall is taken into accont when assigning grades. In its most extreme form, grades are assigned based on a student’s rank in class, placing students in direct competition with each other.
Chilton obviously grades on a curve, fostering a highly competitive environment. Paris is concerned that Rory joining the class, with her excellent academic results, may affect her own grades.