GREENCASTLE, Pa. – A Pennsylvania school district is canceling its first day of class over concerns about student safety during August’s full solar eclipse.

Classes in the Greencastle-Antrim School District were initially scheduled to resume on Monday, August 21, but district superintendent Kendra Trail sent a letter to parents on Monday delaying the start time, WPMT reports.

“When putting together the school calendar, it is hard to anticipate all of the events that could impact the schedule; therefore, when considering our first day of school, we realized a solar eclipse is to occur on Monday, August 21,” Trail wrote.

“The beginning of the eclipse is to occur in our area around 1:15 p.m., with maximum coverage of 80 percent occurring around 2:40 p.m., with the end of the eclipse around 4 p.m.,” the letter read. “Normal dismissal time for our district begins at 2:25 p.m. for our middle and high school students and 3 p.m. for our primary and secondary students.

“Many primary and elementary students will be on the bus until after 4 p.m., especially on the first day of school. Due to the safety risks associated with viewing the eclipse, it is imperative that students are not outdoors during these hours.”

Trial wrote that students will now be expected to attend classes on Jan. 2 to make up for the lost day.

According to the NASA eclipse website, the solar eclipse comes with some risk of eye injuries if students are not properly supervised.

“Exposure of the retina to intense visible light causes damage to its light-sensitive rod and cone cells. The light triggers a series of complex chemical reactions within the cells which damages their ability to respond to a visual stimulus, and in extreme cases, can destroy them. The result is a loss of visual function which may be either temporary or permanent, depending on the severity of the damage,” NASA reports.

“When a person looks repeatedly or for a long time at the Sun without proper protection for the eyes, this photochemical retinal damage may be accompanied by a thermal injury – the high level of visible and near-infrared radiation causes heating that literally cooks the exposed tissue. This thermal injury or photocoagulation destroys the rods and cones, creating a small blind area. The danger to vision is significant because photic retinal injuries occur without any feeling of pain (there are no pain receptors in the retina), and the visual effects do not occur for at least several hours after the damage is done ….”

The learning benefits from students observing the solar eclipse, however, are many.

“A solar eclipse offers students a unique opportunity to see a natural phenomenon that illustrates the basic principles of mathematics and science that are taught through elementary and secondary school,” according to the NASA site. “Teachers can use eclipses to show how the laws of motion and the mathematics of orbital motion can predict the occurrence of eclipses. The use of pinhole cameras and telescopes or binoculars to observe an eclipse leads to an understanding of the optics of these devices. The rise and fall of environmental light levels during an eclipse illustrate the principles of radiometry and photometry, while biology classes can observe the associated behavior of plants and animals. It is also an opportunity for children of school age to contribute actively to scientific research – observations of contact timings at different locations along the eclipse path are useful in refining our knowledge of the orbital motions of the Moon and earth, and sketches and photographs of the solar corona can be used to build a three-dimensional picture of the Sun’s extended atmosphere during the eclipse.”

Of course, Greencastle schools isn’t the only school district canceling classes to protect students from themselves.

Illinois’ Edwardsville District 7 deemed the once in a lifetime event an “environmental hazard” and also canceled classes for the whole day to avoid any potential problems. Edwardsville Superintendent Lynda Andre made the decision, which will require the district to make up the lost instructional time at the end of the year, despite numerous requests from teachers for field trips and viewing sessions.

The district isn’t willing to train its 470 teachers on how to monitor students during the eclipse, she told the Belleville News-Democrat, so she’s leaving the task up to parents.

“To put students outdoors during that time, we can’t account for whether they’ll look at the sun,” she said. “We will not put the students out and just hope they use safe habits until they get home to their parents.”

In other districts, school officials canceled classes after teachers spent months preparing lessons for the eclipse, EAGnews reports.

Regardless, other school districts are providing students with protective eyewear and plan to use the phenomenon to bring science and other subjects to life.

Tirad Local Schools superintendent Leigh Lewis told the News-Democrat students with parental permission slips will learn from the experience alongside their teachers, while parents with safety concerns can keep their children home, if they wish.

“We realize the hardship closing school might have on some households,” she said. “Therefore, we prefer that parents make the choice that suits their needs.”