After receiving their vaccines, will children still need to take precautions to prevent viral spread at school?

While the vaccinations are very effective, especially for preventing severe COVID-19, they do not provide perfect protection.
Until the pandemic is broadly controlled, we need to use all available tools to reduce viral spread in schools and other public settings, including vaccinating everyone who is eligible to receive the vaccine, mask-wearing indoors for everyone older than 2 and in some cases outdoors as well, hand hygiene, physical distancing, improving ventilation in schools when possible, and other mitigation measures.
Reducing viral spread keeps our communities healthy and gives the virus fewer opportunities to mutate in ways that result in dangerous new variants.