This choice of 6 ft made it impossible for schools to try to get back going since there was no way to physically accomplish this.
Fauci admits the pulled the number out of thin air in this video of his testimony under oath (starts about the 1:20 point). Different groups like the Teacher's Union had huge input as to what they wanted (Fauci references "labor unions).
The thing is that they didn't say that they were taking their best guess because then there would have been more push to get the kids back in school and church's open, etc..
Instead, they said that there was evidence....and you can see here after the fact, Fauci admits that there was never evidence for it at all.
With inevitable exposure to all, the only time that any distance would have been meaningful (if it was ever determined scientifically) would have been in the first 2 months to "blunt the curve" to prevent hospitals from being overwhelmed.
Beyond that, if it even did work, it would merely be slowing the development of herd immunity.
Link: https://www.bing.com/videos/riverview/relatedvideo?q=fauci%20lied%20social%20distancing&mid=41284BE7B26892E9D28641284BE7B26892E9D286&ajaxhist=0