HARTFORD — Public school districts can shorten the 2020-21 school year by three days if that time is used at the start to plan.

The unanimous state Board of Education decision will shorten the state-required 180-school day to 177 days.

Commissioner of Education Miguel Cardona said the requirement that districts plan for three separate opening plans — full, hybrid or distance learning — necessitates extra time for staff training to maintain public safety.

A waiver of the requirement is rare and usually requires school districts to try and make up the lost time during the following school year.

“It’s the right thing to do,” Cardona told the board, which met online on Tuesday.

The time can only be used at the start of the school year to both train staff and orient families.

“It is not often that something rises to the occasion, that deserves conversation about whether limiting 180 days is the right thing to do,” Cardona said. “I believe this is one of them.”

The action comes after the 2019-20 school year’s traditional structure was cut short by more than three months with learning becoming a remote experience as the COVID-19 pandemic swept through the state causing a quarantine.

Cardona and Gov. Ned Lamont issued guidance late last month asking school districts to plan for a full, in-person school opening but also contingencies. Lamont said Monday that a more definitive answer to what the school year would look like would be given in August.

Cardona said the challenge is that schools need to be able to change course depending on science.

Districts have until July 24 to submit local plans along with what they think those plans will cost. There is no approval process but there will be a review to ensure they comply with the governor’s orders.

Deputy Commissioner of Education Desi Nesmith told the board about $4 million in federal CARES Act funding will be used to increase connectivity for 10 districts in most need, adding about 12,000 additional devices to close gaps.

The state Board of Education, without taking a vote, informally endorsed the plan, with full knowledge it is a fluid document that is likely to change.

“I think it is important that we stand behind this plan,” said Erin Benham, a board member. “The negativity is getting louder and louder and I think we need to endorse this great work and know that it is a fluid document.”