Under updated guidelines from the state, California school children starting school this fall will need to wear masks when indoors, regardless of vaccination status. Currently, vaccines are available to those 12 and older; many school children will not be vaccinated by the time school starts. (There are some exemptions).
Oakland schools re-opened last spring on a limited basis, allowing for physical distancing (and still masked), but with schools expected to be in-person every day starting in the fall, masking is seen as a compromise to ensure safety and also allowing for more children to be present together.
While some note CA’s guidelines as controversial, being more strict than the federal CDC guidelines, the bottom line is that children will most likely need to wear masks when indoors at schools.