If you have buses at your school, you need to find out EARLY in the day, not the last minute, exactly which kids ride the bus, and if there is more than one bus, which bus they ride. In our district, parents have to sign their kids up with Transportation in order for them to be able to ride the bus, so in theory, it is possible to get a list of the bus riders. Someone at the school at the end of the day, should have the assignment to take the kindergarten kids to their bus and see that they get on it (at my last school, our buses were on the far side of the school. Someone escorted the kindergarten bus kids for the entire year. ). You can’t do that AND dismiss the rest of them, nor can you expect to be able to send them off to the bus by themselves with any reasonable expectation that they will in fact actually make it to the right bus. If the buses pick up in visual line of sight for the teacher it might be feasible.
And this is not a one day thing. Some parents aren’t comfortable with having their kindergartener ride the bus the first day, or even the first few days. I tell them to let me know IN WRITING, the day that the child will begin riding the bus. Do NOT have the child tell me verbally when they are riding the bus. In fact, with any deviation from the norm they should let me know in writing. If a student tells me for example that today, they are not riding the bus, and it’s too late to check at home on the phone, the child WILL ride the bus.