UNDER NEW STATE GUIDELINES issued Tuesday night, Somerville should be preparing to bring students back to school in person next month. It isn’t.

Somerville, a dense urban area outside of Boston, is ranked as “green,” or low-risk, on a new state map measuring COVID-19 rates. The Department of Elementary and Secondary Education says green communities should have full-time in-person learning, or at least a hybrid model if there are extenuating circumstances.

But Somerville already decided to start with fully remote learning, and Mayor Joe Curtatone called the new guidelines “confusing and disappointing.” “To look at a color-coded map and say that should be a bright line as to whether to bring back students, staff, teachers to school really disregards all the other variables we must analyze…when we make these decisions,” Curtatone said.

Gov. Charlie Baker on Tuesday announced a new color-coded system that ranks every city and town based on the prevalence of COVID-19. The Department of Elementary and Secondary Education then issued guidancerecommending that school districts choose an education plan – remote, hybrid, or fully in-person – based on their ranking. The four cities that are red, or highest-risk, should have remote learning. The 29 communities that are yellow, or moderate-risk, should have a hybrid system or a remote one, if there are extenuating circumstances. The remaining lower-risk communities should return in person, either full-time or part-time.

For those low-risk communities, Baker said at a press conference, “I can’t imagine a good reason not to go back, whether it’s full time or some sort of a hybrid.” Baker added, “For all intents and purposes, you meet all the benchmarks that are being used across the country and across New England about whether it’s safe to go back to school.”

Baker’s statement enraged Medford school committee vice chair Paul Ruseau, who says the decision is nowhere near that simple. “If he can’t see any reason, he has literally not even glanced at a public school system,” Ruseau said.

Ruseau cited a shortage of teachers able to come in for health or childcare reasons, school buildings without extra space to accommodate physical distancing rules, old schools that lack proper ventilation, and the need to negotiate terms with unions worried about employee safety.

School officials statewide have been asking for weeks for a metric they can use to determine what system of schooling they should move forward with. But for many, the Baker administration’s guidelines – issued three days before districts must submit their final plans to the state – are too little too late. Many school committees already voted on their plans. Some developed their own metrics in the absence of state guidelines. Ultimately, the decision of which model to use is up to local school committees.

“The metrics are something superintendents have been looking for for quite some time and are welcomed, but I wish they had arrived about three weeks earlier,” said Tom Scott, executive director of the Massachusetts Association of School Superintendents.

Some communities have said they will be reassessing their plans repeatedly, sometimes as often as every two weeks. The guidelines could be a useful measure for those communities. The state guidance acknowledges that while some communities may tweak their fall reopening plans, others may “wait for multiple data reports and allow for further time for consultation before making these updates.”

But at the same time, several school officials said the guidelines ignore the myriad factors that go into reopening a school building.

Medford is planning a hybrid system, with high-needs students and a few grades coming into school two days a week in September, and other grades gradually returning over the next couple of months. By mid-November, all students are expected to be in school two days a week. But Ruseau thinks the prospect of returning to all-remote learning due to an outbreak is more likely than a move to all in-person learning.

For a district to open the right way, Ruseau said, it would need to enlist a range of specialists from epidemiologists to HVAC engineers. He worries that schools are being asked to solve economic, health care, and childcare problems, despite historic underfunding. They are being asked to help kids recover academically and socially from the last few months, and address their mental health challenges, without significantly more money. “It’s fantastical, it boggles the mind that is even a conversation point unless you know nothing about public schools,” Ruseau said.

Curtatone said the state map ignores regional context. Somerville, for example, borders the high-risk community of Chelsea. Residents ride the same transit system and work in the same industries. Not considering that, he said, “makes no sense.”

Curtatone said schools are hampered by a lack of available COVID-19 testing. Some colleges, for example, contracted with private testing labs to constantly test their students, but school districts do not have those resources.

Somerville’s neighbor of Cambridge, another “green” city, plans to keep students in grades four through 12 at home in September, with in-person learning only for special education and English immersion students and students in third grade or younger.

Cambridge developed its own reopening metrics before the state published its map, and the Cambridge metric considers new cases per day, the positive test rate, and the results of sewage monitoring.

Manikka Bowman, vice chair of the Cambridge school committee, said she is happy the state finally released guidelines to help communities determine when it is safe to return, and Cambridge will consider the state guidelines “in concert” with its own, while continuing to be flexible. But Bowman said she voted for the current plan after considering not only the science, but also input from the public related to people’s mental well-being.

“It’s not as easy as saying these are the guidelines, you’re in green, you need to be back in school,” Bowman said. “It doesn’t work that way.”

The late timing of the guidelines is also an issue for communities. Leominster voted a couple of weeks ago to keep students remote.

Leominster school committee chair Eileen Griffin said going back to school fully in person would be impossible due to the need for more teachers and more classrooms to abide by physical distancing guidelines. The school committee voted 5-4 to adopt a remote-only plan instead of a hybrid plan. At a meeting this past Monday, the committee reaffirmed that decision but authorized the superintendent to bring back into the classroom certain high-need populations and vocational students.

“The majority of the people who had voted for it were really concerned about the risks and safety to both students and staff and really felt that they wanted to err on the side of caution to ensure that everything was in place,” said Griffin.

Griffin said she does not know yet if the DESE guidelines, which classify Leominster as low-risk, will change the committee’s mind. “It would have been helpful if we had the information prior to our meeting,” she said.

But she said the school committee could not wait any longer before deciding. “It was important for us to come up with a plan so people could have time to make plans and we’d be able to move forward and give more specific details on how that would look,” Griffin said. “It’s also important for families not to every other week be told something different.”

One of the first communities to vote with the benefit of the new guidelines was the Melrose school committee, which met Tuesday from 6:30 p.m. until after midnight, debating its plan. Even though Melrose was deemed low-risk, school committee chair Ed O’Connell said for him that was simply one metric, in addition to the significant input the district got from teachers’ unions, parents, and others.

“For me personally I just felt there still remained too much uncertainty,” O’Connell said. The new guidance, he said, “didn’t convince me it was safe to go back.” He noted that Melrose has teachers and students from neighboring communities, some of which are yellow. “We’re not in a hermetically sealed green environment,” he said.

Hours after the guidance came out putting Melrose in the “in-person” category, Melrose voted 5-2 to start the year remotely and bring back only a few hundred high-needs students, at least for the first month. “It was a situation with no right answer and no clear course of action. We were called upon to use our judgment and that’s what we did,” O’Connell said.