Today is the last day of school for most Clark County students. Classes were dismissed between 10:30 and 12:30 p.m. at most campuses. The district is urging drivers to use caution around school zones and to obey the posted signs and flashing lights. Seventy year-round elementary schools will still be operating this summer. Meanwhile, graduation ceremonies take place tonight and Thursday night for some valley high schools, including rural campuses and high schools in Boulder City and Laughlin. Other high schools in Las Vegas, Henderson and North Las Vegas will hold their graduation ceremonies next week. Most of the events will take place either at The Orleans Arena or the Thomas and Mack Center.