With the already-delayed start of Boston Public Schools just over four weeks away, Boston Mayor Marty Walsh said Tuesday that there has still been no final decision on whether schools will open on an all-remote learning basis, or on a “hybrid” or “hopscotch” model that would allow students to opt-in to returning to classrooms on a part-time basis.

And the mayor pushed back on criticism by the Boston Teachers Union and members of Boston City Council who are calling on the school district to abandon, for now, plans for in-class learning and to immediately and definitely decide on all-remote learning for at least the start of the school year.

During a press conference Tuesday, Walsh said he and Boston Public Schools Superintendent Brenda Cassellius will likely announce a decision within the next few days. In the meantime, Walsh said, BPS is working to prepare schools for a safe return and are closely monitoring safety indicators, especially infection and hospitalization rates for COVID-19.

Noting that “every family has the choice to begin the year remotely,” Walsh said that the district’s priorities are “safety, quality and equity,” and that “We will be guided by the data as we have been throughout this pandemic.”

Walsh said BPS is refitting classrooms across the district to make sure at least one window in every classroom can be opened, as well as installing more than 30 new HVAC systems and supplying thousands of fans to classrooms.

Walsh has faced steady criticism over a draft plan released by BPS earlier this month, a somewhat revised version of which BPS submitted to state officials Friday.

Members of the Boston Teachers Union have called on the city to abandon the idea of beginning the school year on a hybrid basis, saying the district’s plans aren’t sufficient to keep teachers or students safe.

"We understand that the City wants to weigh it's options, but as we near the reopening of our schools, educators, families and students need to prepare for the academic year," Boston Teachers Union President Jessica Tang said in a statement to WGBH News after the mayor's remarks. "It's time for the City to listen to our school community stakeholders and make the decision to safely restart schools predominantly remotely, while evaluating the evolving situation to safely expand in-person learning for those who most need it.”

Several members of Boston’s City Council have criticized not only the draft plan itself but the continued uncertainty over a final decision.

Boston City Councilor Andrea Campbell, one of several Council members who have called for an all-remote start to classes, said in a statement to WGBH News after the mayor's remarks that she was "shocked and disappointed that we still do not have a decision on reopening but instead have an 80 page document with no decisive plan."

"Every day the district delays this decision, we lose an opportunity to prepare our students for success and our community loses confidence that this school year will be safe and successful," Campbell wrote.

Walsh and Cassellius responded to some of those critiques during an appearance on WGBH News’ Greater Boston, shortly after Walsh’s public remarks and ensuing statements from the BTU’s Tang and Councilor Campbell.

Cassellius said that teachers with underlying conditions that make them vulnerable to coronavirus can take advantage of existing policies like family leave.

Asked by host Jim Braude about teachers who might not have such conditions but who feel scared or anxious to return to classrooms, Cassellius answered, “We’re all feeling some anxiety and I empathize with those teachers and I really understand that this is scary.”

“But I believe if we can guarantee, if we can show them,” that BPS buildings and classrooms are safe, Cassellius said, “If they can get into the buildings and they can see they’re safe and clean and we do have the proper protocols in place, I think they’ll feel more settled.”

Walsh, meanwhile, stood by remarks Tuesday and recently suggesting the objections by the BTU and Council members were “political,” in nature, though sounded a more conciliatory note than he has on some of those occasions.

“For all intents and purposes when we do reopen the schools, coronavirus is still going to be here,” Walsh said. “We're not going to have a vaccine that's going to be able to be distributed to [all] Americans. ... So we're asking people to have the conversation with us right now.”

“Let’s have the conversation at the table,” Walsh said. “Let’s talk about what we’re doing.”