Costs: potentially language learning and communication issues, worse psychological well-being and negative physiological effects.

Benefits: None

https://www.zerohedge.com/covid-19/child-mask-mandates-have-no-clear-benefits-and-cause-harm-bmj-review-finds

AND

Child mask mandates for COVID-19: a systematic review

https://adc.bmj.com/content/early/2023/12/06/archdischild-2023-326215