Editor's note: Article updated at 12:44 p.m. on Friday.
Each search was a planned lockdown based on requests from the schools to search those buildings, Flynn said.
"Those were planned events, nothing to be frightened about and everything turned out just fine," he said.
Arlington High School interim principal Mary Villano said that the school runs a practice lockdown every year and Friday's served as this year's practice run. The K-9 units and officers from other communities get a chance to familiarize themselves with the building in case of an actual emergency.
"We’re not looking for anything in particular, nothing has come up that we think we need to look for … just kind of a routine experience," Villano said.
Flynn said no items were confiscated during the search and police are waiting to receive reports back from the dog handlers.
"Everything went off without incident," he said.