The measure will be adopted by the country’s 17 regions, which manage education autonomously, as part of nationwide efforts to stem the spread of coronavirus.
It is part of a series of standardised guidelines agreed in a meeting with central authorities. Previously, masks were only required for pupils aged 12 and above by some Spanish regions.
Pupils will receive a daily body temperature check, they must wash their hands at least five times per day, and classrooms will need frequent ventilation, the government said.
“Bubble-classrooms”, where pupils only socialise with a limited number of peers, will be key to identifying contacts. That allows localised quarantines if there is a positive test, rather than the closure of entire schools.
Parent and teachers have expressed concern about schools reopening amid new waves of outbreaks since the country emerged from a strict lockdown.