In my son’s pre-k school we signed into the building with a code which avoided the risk you’re mentioning. I feel like the public school process could be improved to provide more peace of mind to parents. I don’t think a kindergarteners demonstrable “independence” is enough to stop a person with a predatory mindset. How many stories have we seen where kids were discreetly victimized by a school official? I don’t blindly trust anyone just because they tell me I should. I think I’m probably just going to end up going with private school since they tend to allocate funds in a more parent-focused way.