Does CDC guidance lack studies or data showing student masking reduces COVID-19 infections?

The Centers for Disease Control website is peppered with references to studies that show mask use by students is associated with lower COVID-19 infection rates, contrary to a claim in a social media post.

A study in North Carolina looked at 11 school districts that adhered to multiple prevention strategies, including universal mask use. It reported low school-related transmission and "breaches in mask use likely explained the few instances of in-school spread of SARS-CoV-2," according to the CDC.

A similar study of elementary schools in Utah with high student mask use found low school-related transmission.

And a Florida study found higher infection rates in districts with no mask requirement. That study said: "Success in preventing the introduction of SARS-CoV-2 into schools depends upon controlling community transmission and adhering to mitigation measures in schools, particularly masking, physical distancing, testing, and increasing room air ventilation."