By that logic we shouldn't let kids learn to swim because of accidental drownings and keep them away from water, it can be safe with supervision but kids still drown even when there are lifeguards present. The point is to educate kids on something they have a chance at encountering in their lives, and in an off chance they do happen to stumble on a loaded firearm left out they know not to touch it. Kids who pick up guns think they're toys because they only know they're "bad" and dont know how dangerous they are because they are uneducated. Its similar to pouring water on a grease fire, people hear they aren't supposed to do it but dont know how bad it can get and do it anyways.

Also any beginner firearms class starts with classroom time where guns and ammo aren't present, then when the instructor thinks everyone is ready they'll hand them the gun, which for an elementary school would be a single shot .22 or air gun, not anything semiautomatic. In elementary schools kids wouldn't touch a gun for at least a couple of weeks with how long classes normally run.

Also it takes a trained locksmith to crack safes like this because drills need to be involved, some elementary school kid who watched a youtube video wouldn't be able to open it. Also any insurance company wouldn't allow any other type of safe. Even if they could get fingerprints, which is illogical and hollywoodesque, there would be six numbers that have the same "beep" so they couldn't go off of sound.With a 6 digit combo there would be over 85 thousand possible combinations. what you're saying kids can do is unrealistic when it comes to safe cracking.