Gov. Larry Hogan urged school systems to make plans to start bringing students back for in-person classes by March, saying he will explore consequences for districts that refuse and calling on teachers unions to drop their objections.

“A growing consensus has emerged, both here in Maryland and across the country, that there is no public health reason for county school boards to keep students out of schools,” Hogan said at a news conference at St. John’s College in Annapolis on Thursday.

Local school officials were not briefed in advance on what Hogan would say, but at least two major school systems in the Baltimore region — Baltimore and Harford counties — immediately said they would shift plans to reopen for at least some students by March 1.

Pointing to data that shows the state’s students are falling behind academically, Hogan called on school systems to use either of two models for in-person classes approved by state health officials as safe under current conditions. And he said he will announce further steps to accelerate vaccinations next week.

The announcement comes amid news of a new, more contagious strain of the coronavirus and a surge in infections across the state.

Hogan, a Republican, acknowledged he cannot order the schools to reopen, but “if school systems do not immediately begin a good faith effort to return to classrooms, we will explore every legal avenue at our disposal.”

He referenced situations across the country: Chicago is cutting off pay to teachers who refuse to teach in person, South Carolina is yanking licenses and Ohio is only vaccinating teachers who commit to returning to classrooms.

Hogan cited President Joe Biden’s support for reopening schools. The Democrat has set a goal of having most K-8 schools reopen in his first 100 days, and he’s ordering the departments of Education and Health and Human Services to provide clear guidance for reopening schools safely.

“Far too many students remain unable to thrive in such an environment and there can be no debating that online learning has taken an unmistakable toll on students, families and educators,” Hogan said.

Hogan and Karen Salmon, the state school superintendent, also sent a letter to the head of the state teachers’ union telling her “roadblocks to resuming in-person instruction must cease.”

“We need to follow the science, and we must use the case studies from around

the globe as a testament to the successful and safe return of students to their schools,” they wrote.

Maryland State Education Association President Cheryl Bost said that state leaders have not worked collaboratively with the teachers union or sought their opinions since August. Thursday’s letter from Hogan and Salmon arrived minutes before the press conference began and was Hogan’s first correspondence with the union that represents most of the state’s teachers.

Bost said the union has been working with local school systems to try to improve conditions to make it safe for teachers to return, but she said the union wants teachers to have both shots of the vaccine before they go into classrooms.

“After hearing a lot of unifying conversation yesterday, I was disappointed that he would take legal action when the teachers are working so hard,” Bost said.

Christina Duncan Evans, a representative in the Baltimore Teachers Union, said Hogan is asking teachers and school staff “to take a big risk with their lives and the lives of their families.” She also said it is difficult for teachers to teach online and in-person at the same time.

“If the governor is focusing his energy on punishing people for non-compliance, then that is a very misguided approach,” Duncan Evans said.

Salmon and Hogannoted that failing grades for students throughout Maryland were far higher in the first term of the current academic year than in the previous year and that there has been a disproportionate effect on students of color and students from families with low incomes.

Dr. Jinlene Chan, Maryland’s acting deputy secretary for public health, said that studies show spread within schools is relatively low if schools abide by proper mitigation and safety measures.

“There is little evidence that school reopening is a major driver of overall community spread,” she said.

Brown University economist Emily Oster and researchers at Johns Hopkins University have concluded the risk of opening schools is tied to the prevalence of community spread. The more coronavirus cases a community has, the likelier it is a community will have cases in schools. But they have not found opening schools accelerates the spread of the virus.

State guidelines for schools have been revised with options that state officials deem safe even at current levels of spread, Chan said.

The first option calls for daily in-person learning for students with disabilities, special learning needs, those who’ve struggled remotely and high school students in career and technical courses; daily in-person instruction for elementary students (unless high levels of community spread requires hybrid learning); and hybrid for middle and high school students.

The other option would offer daily in-person instruction for those with “unique educational needs,” phased-in hybrid learning for elementary students, and remote learning for middle and high schools.

Throughout the pandemic, few students in suburban Maryland counties have been back inside a public school, despite months when COVID-19 rates were relatively low and other districts across the nation — such as New York City and Providence, Rhode Island — were opening back up. Most districts in the state remain closed.

Carroll County has reopened, Baltimore City is expanding in-person instruction on Feb. 15 and Anne Arundel had planned to reopen by March 1.

Baltimore County school officials said in a statement they would “review today’s announcement and adjust our reopening plan accordingly.” Baltimore County has been closed since March but was working on a reopening plan.

Harford schools had a plan in place to return students to classrooms under a hybrid model once COVID-19 metrics in the county improved, as it had done for a few weeks in October and November before cases spiked.

Logistically, Harford County Superintendent Sean Bulson said, the school system should be able to meet the state’s March 1 deadline to have kids back in the classroom. County school staff will try to present a plan to the school board Monday night to do that, he said.

“If there is an expectation that we follow the social distancing, but a similar expectation that we put students in any sort of daily instruction for any overarching group, then we have a conflict in the guidance that we need to work through,” Bulson said.

Howard County had voted late last year to stay virtual through at least mid-April, but schools Superintendent Michael Martirano and the Board of Education discussed during a Thursday night meeting about whether and how they would speed up their timeline to develop and approve a hybrid model.

Hogan’s announcement follows a meeting his staff had less than a week ago with parents from around the state who have been agitating for reopening schools. They greeted the announcement with joy.

“I appreciate Gov. Hogan’s strong stance and that someone needs to be held accountable,” said Amy Adams, a Baltimore County parent, who added that parents appreciate the efforts teachers have made over the past year.

“I hope that everybody can come to a meeting point and do what is good for the children,” said Carroll County parent Katie Haman. “This has been going on far too long.”

Teachers are newly eligible to be vaccinated during Phase 1B of the state’s vaccination plan, which began this week. But that group also includes adults at least 75 years old, the homeless, people who live in group homes and child care workers.

Many people now eligible for the vaccine have reported difficulty getting appointments.

Russell Leone, president of the Teachers Association of Anne Arundel County, said the union has been working toward a return to in-person learning when it is safe and when teachers have been fully vaccinated.

“I’m concerned about the availability, because it seems like the governor said that there’s plenty available,” he said. “Teachers are still waiting, they’re still on lists.”

Baltimore City’s school system started a vaccination program this week, but at the current rate of 500 employees per week, it will take five months to vaccinate all 10,000 city teachers.

Chan urged all school employees to get a vaccine when available, but said that shouldn’t be a factor in reopening decisions.

“I would emphasize, that school reopening decisions should not be based on the availability of vaccination or the level of vaccination among staff,” she said.

Hogan said he spoke with Biden and the new head of the federal coronavirus task force, and expects more steps on vaccinations from them in the coming days

Baltimore Sun Media Group reporters David Anderson, Wayne Carter, Jacob Calvin Meyer and Lilly Price contributed to this article.