BOSTON (SHNS) – As students returned to classes Monday amid a continued surge in COVID-19 cases, Gov. Charlie Baker kicked off his week with an early morning press conference where he forecast “a challenging period of time” but called the reopening of schools a “terrifically positive sign about the hard work that so many people around the commonwealth are doing every single day to make sure kids get the education they’re entitled to.”

Baker visited Salem’s Saltonstall School, where he said the “vast majority” of Massachusetts districts are open Monday after the holiday break. Some schools opened late or remained closed, including in cases where school officials said they wanted to use the time to test staff using state-secured kits that arrived later than anticipated or to assess staff availability levels.

“We fully anticipate that we’re going to have staffing vacancies or shortages due to COVID,” Salem Mayor Kim Driscoll said. “Frankly, that was the case before the holiday as well.”

Baker said issues around staff and faculty “will be complicated” and the state “will do whatever we can to help people work their way through it.”

“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,” he said. “And that can be, I think, 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.”

Fueled by the omicron variant, COVID-19 case counts have spiked in Massachusetts and nationally, and the state’s daily number of new infections repeatedly climbed to new record highs in late December, while schools were on break.

On Friday, the Department of Public Health reported 21,397 new, confirmed cases of COVID-19 and said 1,954 people were hospitalized with the virus. The seven-day average test positivity rate has skyrocketed to 18.42 percent, from 4.87 percent on Dec. 1 and 1.75 percent on Nov. 1.

Demand for testing has also soared, with long lines reported at test sites and pharmacies regularly selling out of home test kits.

Municipalities, school districts and other public entities are now able to purchase rapid tests through state contracts with three manufacturers — Ellume Limited, iHealth and Intrivo — that the Baker administration announced last week.

“Rapid tests are the most difficult thing to procure in bulk quantities right now,” Driscoll said. “We’re chasing them. Thanks to the state contract, we’re hoping to get them here within a week. We’ve ordered some prior. They’re hard to get.”

Baker said there has been “a lot of active traffic” on the state’s website for buying those tests, and that he expects the kits to “start arriving later this week.”

Last week, the Department of Elementary and Secondary Education also announced plans to provide districts enough rapid home test kits to distribute two tests to each school staffer so they could take one before returning to work.

The test shipment was expected to arrive in Massachusetts by Thursday, Dec. 30, but on Friday evening, Executive Office of Education spokeswoman Colleen Quinn said the original order was delayed due to “supply chain availability” and DESE “worked quickly to find an alternative supply.”

Quinn said the department planned to distribute more than 227,000 rapid tests to districts Saturday and Sunday, thanking test manufacturer iHealth for stepping in to supply tests and FedEx for helping facilitate the shipment. DESE’s latest COVID-19 case report showed approximately 140,000 staff members working in schools across the state.

The approach to testing and the return from the winter break has varied across the state.

Brockton left its high school closed Monday, with other city schools opening on a two-hour delay that district officials said would allow time to “assess staff absences that may be submitted in the morning.” Woburn also delayed the start of its school day by two hours, a move intended to allow time for testing and ensure appropriate staffing.

Cambridge is keeping its schools shuttered both Monday and Tuesday, a plan that involves offering PCR tests — those involving lab work instead of the rapid antigen tests — to students on Monday with the results expected back Tuesday. Ipswich officials said their schools were closed Monday “for a ‘snow day,'” and that they would use the time to distribute test kits and masks provided by the state.

“There was all kinds of talk last week about high school wouldn’t open in Massachusetts today,” Baker said. “School did, pretty much across the Commonwealth. There are a very small number of districts that aren’t in school. Some started late, but the vast majority of the school districts in Massachusetts — thanks to the hard work of so many people who were part of those school districts — are open today.”

The American Federation of Teachers Massachusetts had called for the new year to start with a period of remote learning “until the current wave of infections abates,” and the Massachusetts Teachers Association had said that schools should stay closed Monday except for staff COVID testing.

“We recognize that delaying some students’ return to school poses challenges for families. But if there were a blizzard on Sunday evening, nobody would question the wisdom of declaring Monday a snow day,” MTA President Merrie Najimy said in a Friday statement. “With the omicron variant spreading and COVID-19 positivity rates in the state surpassing 16 percent in the most recent seven-day average — and with Massachusetts now reporting more than 1 million coronavirus cases since the start of the pandemic — it is fair to say that the health and safety risks we face from COVID-19 far surpass those presented by a nor’easter.”

Baker has stressed the importance of in-person instruction and said Monday that districts “do need to provide their kids with 180 days of in person education this year” and that districts can use snow days if they are not open at some point during the year.

The Department of Elementary and Secondary Education no longer counts remote instruction toward the amount of student learning time it requires annually.

“We said for quite a while, since the beginning of the school year — in fact, all the way back to last spring — that it was critically important for kids to be in school for a number of reasons,” Baker said. “Some of it has to do with educational development, but a lot of it has to do with social development, human development, and frankly, in many cases, especially for some of the older kids, just their mental health status generally,” Baker said.

Districts are also in different places when it comes to masking in schools. An indoor mask mandate remains in effect in K-12 schools through at least Jan. 15, but DESE allows schools to lift that requirement for vaccinated individuals if they first demonstrate a COVID-19 vaccination rate of at least 80 percent.

Cohasset High School is among the schools that received state approval to relax its mask mandate and as of Dec. 6 made it optional for vaccinated individuals to wear a face-covering in most settings. Superintendent Patrick Sullivan wrote in an online message that the district was “maintaining our current mask status” in the new year, leaving that policy in place.

Meanwhile, in Worcester, which still has a mask mandate, students were advised on Friday to bring two masks with them to school each day. Worcester on Monday also put in place a new policy limiting attendance at certain athletic events.

The Department of Public Health advises vaccinated and unvaccinated individuals alike to wear masks in indoor spaces. Education officials have characterized the DESE policy, with districts able to lift or reinstate mask mandates as they choose past the 80 percent vaccination threshold, as a matter of local control.