A 20-year-old man and a juvenile were arrested after allegedly making an unspecified threat that sent students at Lexington High School home early Thursday, police said. The specific nature of the threat and the circumstances surrounding it are not being released due to the investigation, police said. Myles Fulton Penniman, 20, of Lexington and a juvenile resident of Belmont were arrested off-campus, police said. The two are charged with threatening a school and disrupting a school. Lexington police and school administration dismissed all students and staff at 1 p.m. and closed the campus for the rest of the day, police said.