Same as an airport would be a bit much, I think.
My son's high school has only two entrances to enter and exit. They are guarded by police for a half hour before school starts and a half hour after school starts. These are double doors, that is, two doors with a ten foot space in between the doors. After the police leave the doors are locked to outsiders.
There are cameras covering the inside, outside, and space between these doors. Lockers are subject to searches at any time, for any reason.
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Yes, all schools need minimal entrances/exits. The shooters need to be stopped BEFORE they enter and I would add metal detectors. Security needs to be beefed up with volunteer retired cops or military with added training for the particular environment specific to schools. I have heard some good suggestions from security people as to deal with the problem and to my mind it can effectively be dealt with.