Back when public schools were overwhelmingly Christian, scheduling religious holidays meant closing for Christmas and, in some places, for Jewish high holidays. As American school populations change, deciding for which religious holidays schools should close and on what basis becomes more complex.
According to Anti-Defamation League religious freedom counsel David Barkey, consistently with the First Amendment's Establishment Clause, "[p]ublic schools can't close to observe a holiday, but can if there's an appropriate secular reason. The reason usually is the level of absenteeism" that would hamper schooling.
Philadelphia's Mayor Jim Kenney suggested a different standard in announcing the city's decision to close public schools for Muslim holidays. Rather than focusing on practical need, Kenney explained: "Our city was built on the idea that ... the city welcomes all to worship and practice the faiths of our culture or our choosing[.] ... We have to take into account how society sometimes ostracizes and eliminates people from the mainstream[.]" In other words, schools should close on minorities' religious holidays so their adherents feel accepted.