I sure hope nobody from the NEA reads your post, for I fear a hijacking of your idea would be in the offing! (As in, let’s take away from the intelligent and diligent students’ excellent grades, and give a portion to the lazy or less gifted children, and then they will all have equally good grades, Kumbayah....)
This is an example conservative students can use in their social studies classes to illustrate a basic difference between socialism and capitalism.
Do we want to pool all our grades in this class and give everyone the resulting average? (Only poor performing students will vote for it.)
Then ask if the hard working students will continue to work hard if they know the fruits of their labors will be taken away from them. (Generally, no. Some students will continue to learn for their own sakes, but why bother turning in the homework?)
So what happens to the class average? It declines sharply.
Now who (other than the very weakest students) wants socialized grades?