School districts in several states are canceling classes on April 8, prioritizing concerns about protecting students from a total solar eclipse over a unique learning opportunity that won’t be available again for 20 years.

As millions prepare to flock to a path of totality that will stretch from Mexico through 10 U.S. states and into Canada next month, hundreds of school districts are canceling classes and setting early dismissals to prevent any issues during the darkness, Newsweek reports.

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In Pittsburgh, where the April 8 eclipse will take place between 2 p.m. and 4:30 p.m., “school leaders say they are concerned that some students might try to catch a glimpse and harm their eyes,” according to WTAE.

The result is several area school districts canceling classes for the day, while others run by the Catholic Diocese of Pittsburgh are moving to flexible instruction from home.

States most impacted by the eclipse include Texas, Oklahoma, Arkansas, Missouri, Illinois, Indiana, Ohio, New York, Pennsylvania, Vermont, New Hampshire and Maine.

In Indiana, at least 25 school districts have already canceled classes for the eclipse, while 16 others will move to remote learning, and one will have a two-hour early release, WRTV reports.

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About 90 Ohio districts have also canceled classes, with three districts and Kent State University moving to remote instruction.

In New York, where dozens of districts are keeping kids home, school officials have cited concerns about crowds and heavy traffic during the eclipse for shutting schools down.

“With the extra added traffic and number of events being planned for the area, the district was concerned about safely transporting students to and from school that day. School districts in other regions of the country that have experienced total eclipses like this have encountered those issues and the district decided to make the switch,” Meghan Piper, spokeswoman for the Liverpool School District, told WSYR.

Other states with significant numbers of eclipse-related school closures include Texas, Vermont, and Maine, according to Newsweek.

“You know what’s predicted is around 150,000 visitors to the area, and to put our students and staff even out on the roads there, it seems better just to have them in a place where they’re safe and we’re not adding to the confusion on the roads,” Essex-Westford School District Superintendent Beth Cobb told Maine Public Radio.

Elsewhere, Brandywine Springs seventh grade science teacher Peter Kelly and others are preparing for “a wonderful and exciting moment” that won’t occur again in the contiguous U.S. until 2044.

“There are no screens involved,” he told Delaware Online. “They can experience it live. And it’s a great opportunity for learning and education because it can really have them think about their place in space.”

Kelly started discussions with his school administration last year, and eventually landed grant funding to ensure all students will have protective solar glasses for viewing what will be a partial eclipse in Delaware.

“All my classes that day: We’ll talk about the eclipse,” he said.

It’s a similar situation at Lorewood Grove Elementary, where STEM coordinator Kendra Moritz Rosner is already preparing for the special learning opportunity by advising her colleagues on viewing the eclipse safely.

“It turns out, as a school, we’re going to go ahead and do this,” she told Delaware Online. “So while I’m kind of bringing the ‘What is this exactly that we’re going to see in the sky,’ all of the teachers – at least third, fourth and fifth – are going to get the kids ready to actually go outside. And as long as it’s a beautiful day, we’ll be able to see the solar eclipse.”