Memorial Day is observed today (though the actual day is Thursday), and there are no classes today. It is the symbolic beginning to the summer season.
Memorial Day is an American holiday, observed on the last Monday of May, honoring the men and women who died while serving in the U.S. military. Originally known as Decoration Day, it originated in the years following the Civil War and became an official federal holiday in 1971. Many Americans observe Memorial Day by visiting cemeteries or memorials, holding family gatherings and participating in parades. [History.com]