Self selection. These are the motivated kids. They're not being held back by a classroom of unmotivated, slow learners.
Then this is clearly the fault of the government school!
The government school is **forcing** motivated students into classrooms where learning is impossible. Whose fault is that?
The kids? NO!
The parents? NO!
The government school? Yes!
The government teachers and principal who cooperate with an impossible system? Yes!