The problem most people don’t mention is you need to rope public school into the same equation or else you’re leaving that entire, extremely large, workforce out which involves maintenance, custodians, IT, nurses, useless administration, teachers, etc etc etc.
No one said everybody had to work the same four days. If one custodian works Monday - Thursday and another works Tuesday - Friday, that still covers a full 5 day week. The whole reason for a 4 day work week is that, right now, life is all work all the time. If you work a 9-5 Monday - Friday and you need to go to the doctor, who is only open 9-5 Monday - Friday, the only way to see them is to take time off of work.