We Jews do not attend school on our high holy days of Rosh Hashanah and Yom Kippur. Those days are considered excused absences. Public schools remain open because most students are not Jews and the absenteeism is minimal.

Christmas and Easter are Christian high holy days. If Christians do not attend school on those days attendance would be so sparse that it is not worth keeping schools open. Also, most teachers are Christian so there would be too few teachers.