Is it right to lock children out of the school at recess and noon?

My kids ages 6 and 8 go to school in the country. School has about 300 students from Kindergarten to grade 8. School had some vandalism and threats last year. Now they are locking the doors at recess and noon so that the students have to ask a teacher to unlock,delaying entry time, and let them in. Is it right? I think not!! what worries me is last year a dog came onto school property(turned out to be friendly dog) but, could have bitten kids. What if someone were to go there with bad intentions...even seconds to run all the way around to the office doors or wait for someone to come unlock and let them in could be too late. There is currently an escaped murderer in the province, the police don't know his whereabouts. What can I do to get the school to keep the doors unlocked for the students??? Is this being done at any other schools?