No seat belts on the bus here at all. The seat backs are high and cushioned. I'm all for safety, but I don't think seat belts on a bus are the answer. How can a driver make sure the kids keep them on AND drive the bus? The school district would have to have a bus aide on each bus. I guess in a district where there's a separate bus for preschool/K kids, it would be do-able.
Still, the driver should be waiting until the kid is sitting down to pull out, especially on a bus that's for younger kids. I think you were right to put in a call.