[education] TIL about Bloom's 2 Sigma problem courtesy of @af2dd916 

This tracks w/ what we've observed with our kids .... when they started in virtual school 3 years ago, we were surprised at what they did not know. Virtual school was student working w/ parent checking & teaching study skills, etc. Now the kids are in physical school ... & we still need to check, study skills, review, comms, etc. The TIME.

Mekka's thread: https://hachyderm.io/@mekkaokereke/111143265065240342 
Bloom's 2 sigma: https://en.m.wikipedia.org/wiki/Bloom%27s_2_sigma_problem