I would cheer, and encourage that teacger.
In the real world, the one that teachers are preparing these children for, those who strive to achieve, rise above the rest, those who do not, remain in the pack.
Teach the kids to strive for excellence, not to hide behind mediocrity.
Those few that achieve the "A" grades, worked hard, the others did not.
I don't believe in teaching down to the lowest common point.