Some people are on a different educational level than others, and may comprehend topics at different speeds. The public schooling system does not take this into affect, and can cause people to fail school disregarding the amount of effort they put in.
No matter how hard the students work in a forced curve school, some will fail. If all students work at 100% maximum capacity, they will all have perfect scores and some students would have to be failed due to the curve, possibly at random.
This is a broad, declarative statement with no support whatsoever. It fails to take into account a myriad of relevant factors that impact a student's success, and also fails to consider the possibility of corruption within education institutions.
Google: "how home life affects student performance"
Google: "college cheating"
Google: "NCAA college athletes cheating"
Google: "effect of socioeconomic status on education"