My kids are in elementary school. So far this school year, which has only been about three weeks, they have ridden bikes with other neighborhood kids, and with my wife and another mom riding with them every day. It's a short ride, probably a little less than a mile, and it's 75% gravel MUP and 25% sidewalk with crossing guards and the occasional police cruiser parked in front of the school, which is in a quiet residential neighborhood.

Our kids have cheap cable "word locks" with four-digit words to unlock them. I figure someone could probably cut through those locks with nail clippers, but I doubt bike thieves target kids' bikes or schools, and I think it's a good habit for them to always lock their bikes when they will leave them unattended.

Our school has three really long bike racks, and right now there are so many kids riding bikes to school that my wife reports some kids are locking their bikes together in pairs or groups of three near the racks, but not attached to them, because the racks are so crowded.