normally you're supposed to actually demand proof that something is a net positive before you start mandating it, instead of saying "it's not exactly burdensome, why not?", and then going ahead and doing it.
shirts and shoes don't obscure faces, which are used to communicate nonverbally. one of the main advantages of public/private schooling over homeschooling (though there's obviously ways to mitigate this for homeschoolers) is the social interactions between children are valuable in teaching them basic social skills more or less organically.
you have to stop and think about nth-order effects when making broad sweeping authoritarianesque mandates like this, it's never as simple as, "well, they have to wear shirts and shoes to school don't they? how are masks any different?"