A NUMBER OF SCHOOL DISTRICTS didn’t open on Monday because of concerns about COVID, but Gov. Charlie Baker said none of them will be exempted from in-person learning requirements.

“The rules here are pretty simple,” he said at a press conference at the Saltonstall School in Salem with Salem Mayor Kim Driscoll. “We count in-person school as school. If a school district is not open at some point over the course of the year, they can use snow days until they run out of snow days but they do need to provide their kids with 180 days of in-person education this year. We’ll do whatever we can to help them deliver on that.”

Last week, as the holidays came to an end, the Massachusetts Teachers Association called for putting off the reopening of schools on Monday until more rapid COVID tests could be delivered to school districts and to give the districts more time to test teachers and students. The situation became more problematic when supply chain issues delayed the delivery of more than 227,000 rapid tests to school districts until Saturday and Sunday. (The state has also distributed 6 million KN95 masks to schools across the state.)

According to media reports, a number of schools did not open on Monday, including Brookline, Burlington, Cambridge, Ipswich, Lawrence, Lexington, Randolph, Sharon, and Wareham. A handful of schools, including Brockton, Lincoln-Sudbury, Newburyport, Somerville, Waltham, and Woburn, delayed the opening of school for several hours to allow teachers and staff to be tested.

“There was all kinds of talk last week about how schools wouldn’t open in Massachusetts today. But schools did, pretty much across the Commonwealth,” Baker said.

Driscoll, the Salem mayor, predicted a “tough couple of weeks ahead,” but said it’s important to keep kids in school. She compared virtual learning to playing basketball underwater.

Driscoll said Salem received a shipment of rapid tests from the state and placed an order for more tests that should be arriving within a week. Baker also said more tests should be arriving under a state-negotiated contract arrangement later this week.

The governor said staffing levels at schools are a concern. “I do take some comfort in the fact that most cities and towns and most school districts have not spent the vast majority of the federal money they received to support their educational programming during this school year and that can be a terrific tool to help people figure out how to bring people in to deal with some of the issues they have around staff as the year goes on,” he said.