Massachusetts Gov. Charlie Baker is pushing for more school districts to adopt in-house COVID-19 screening as they bring students back for classroom learning this spring.

Baker appeared at the Nock-Molin Middle School in Newburyport to tour the school's pool testing operation and reopened in-class learning Friday morning.

Baker's pool testing program, launched in January, allows schools to test samples from groups of students and teachers for infection. When a positive result is found, each member of the group is then tested to find any infected individuals The method is seen as a way to screen groups like school pods and whole classes using minimal laboratory resources.

"There are hundreds of school districts and schools at this point and hundreds of thousands of kids and staff who are currently doing this and we have the resources and the capability to do this for pretty much everybody," Baker said.

Baker said part of the reason for coming to Newburyport was to spotlight the school's testing program to show it as an example of how districts can adopt pool testing.

"It's a really effective way of dealing with one of the major questions people have generally about this stuff, which is 'what's going on in my building every week,'" Baker said.

Teachers unions have resisted Baker's calls to return to in-person learning and lobbied to be prioritized in the state's vaccination plan before schools reopen. Baker has insisted that schools do not pose much of a transmission threat and that pool testing is a way to show the settings are safe.

Baker and Elementary and Secondary Education Commissioner Jeffrey Riley laid out a plan Tuesday to return K-5 students to in-person classes by April.