For one day every September, elementary schools here open their cafeterias for a special group of people: students’ grandparents.The date is in honor of Grandparents Day. The day officially isn’t until Sunday, but since schools are closed over the weekend, school staff serve up lunch for grandparents so they can enjoy a meal with their grand-kids.North Elementary School (NES) students and their grandparents celebrated the day a little early Thursday. The lunch hour is broken up into three shifts for third, fourth and fifth graders.South Elementary School students are celebrating Grandparents Day with lunch from 11 a.m. until 1 p.m.,