Massachusetts school buildings will remain closed to students for the rest of this school year and non-emergency child care programs will stay shuttered until June 29, Gov. Charlie Baker announced Tuesday, the latest dramatic steps aimed at preventing a rebound in COVID-19 transmission.

Baker said state officials and educators hoped to welcome K-12 public and private school students back before summer, but the administration decided the risk of setting off a new flurry of infections -- particularly because those without symptoms can still spread the virus -- is too great to resume in-person instruction.

"It's the right thing to do considering the facts on the ground associated with the COVID-19 pandemic. At this point in time, there is no authoritative guidance or advisory with respect to how to operate schools safely and how to get students to and from schools safely," he told reporters at a daily press briefing. "We believe students therefore cannot safely return to school and avoid the risk of transmitting the virus to others."

Schools have been closed since March 17, and the most recent order from Baker would have kept students out until at least May 4.

The governor and Education Commissioner Jeff Riley stressed that Tuesday's order does not immediately end the school year. Districts will still be asked to offer remote learning to all students, and many end-of-year activities such as graduations will likely be canceled or shifted online.

Extending closures through the year "gives us additional time" to draft plans for reopening buildings, Riley said, a process that will likely result in different school experiences once students do return.

Officials acknowledged the challenge of educating students from a distance, particularly because some households do not have access to a computer or to high-speed internet needed for classroom videoconferences.

The state will issue guidance this week about how to achieve education goals amid the circumstances.

Riley said officials may not know if the disruption will lead to a dropoff in MCAS scores or other performance metrics "for a few years."

"What we've asked districts to do is to track students that may have fallen off the grid," he said. "They can't be found, for whatever reason, maybe they moved out of state or maybe the phone service isn't in, and try to identify the kids that we are most worried about going forward so that we can offer remedial supports."

On April 10, Baker signed a law allowing Education Commissioner Jeff Riley to vacate MCAS testing for the year and instructing the Department of Elementary and Secondary Education to modify or waive graduation requirements.

It was not clear Tuesday if schools will be able to offer in-person instruction over the summer or must wait until the fall. In response to a question about plans for summer school, Riley said, "I think it's too early to say right now, and that will be another meeting."

Most child care programs have also been halted for weeks following a separate order that took effect March 23. Health care workers and other front-line essential employees have been able to access coverage through 523 emergency facilities opened up for their children, but many parents have had to absorb the change in routine at home.

That status quo will now remain in place until nearly July.

"We know that the lack of child care for many families has created an unanticipated burden and it's hard to look after young children and balance the demands of working at home under the same roof, but maintaining this structure is the best way to keep our kids and our providers safe from the spread of this insidious disease," Baker said. "In the coming months, we'll be working toward slowly restoring child care capacity for both family child care and center-based programs once it can be done safely."

Until facilities reopen, the state will continue to pay subsidies to providers based on their enrollment before the pandemic began, Baker said.

In another announcement Tuesday, Lt. Gov. Karyn Polito said the state Department of Higher Education will defer scheduled repayments for its no-interest loan program until the middle of July, a four-month pause that affects about 12,000 students.

Before Tuesday's announcement, schools had been ordered to remain shut down until May 4, the same expiration date for a separate order closing non-essential businesses. Baker did not say directly Tuesday if he planned to extend the business decision as well, emphasizing that his attention in the short term is on "managing our way through the surge."

Early Education and Care Commissioner Samantha Aigner-Treworgy hinted that keeping child care centers closed allows the administration to align their reopening with a broader return to employment.

"There are plenty of businesses that are open now that aren't relying on the daycare programming to operate," Baker said when asked if businesses could reopen before child care does. "There are many that would benefit from it if we were able to do so. I think, obviously, we're going to have to align a bunch of different pieces and parts as we go forward."

Although new cases of the highly infectious illness have declined slightly in recent days, Baker said the state remains in the surge and that it is too soon to draw conclusions about trends. He described COVID-19 as an "insidious and at times invisible virus."

Total confirmed cases in Massachusetts are likely to surpass 40,000 when the Department of Public Health publishes daily figures later Tuesday afternoon, and deaths could rise past 2,000.

The decision to extend school and day care closures came as Baker stressed the importance of continued social distancing practices. He repeated past warnings against rushing to revive economic activity.

"I'll be damned if the way this works is we go through this thing, we flatten the curve, we do all the stuff we're supposed to do, and then we run up again in the fall because we don't handle the reentry, the reopening, in a way that actually works and makes sense and keeps people safe," Baker said.

"This is difficult," he added. "It's also purposeful and in many cases and in many ways, it's worked, and we should all remember that. The last thing we should do is give this insidious and somewhat invisible virus the opportunity to breath on a go-forward basis."