A quick read of OH law suggests driver is well entitled to make signals.
I'd pay keen attention to whether you turned more than 10 feet away from bus--to proceed beyond that point to this layman seems to trigger issue that you failed to stop.
4511.75 Stopping for stopped school bus.
(A) The driver of a vehicle, streetcar, or trackless trolley upon meeting or overtaking from either direction any school bus stopped for the purpose of receiving or discharging any school child, person attending programs offered by community boards of mental health and county boards of developmental disabilities, or child attending a program offered by a head start agency, shall stop at least ten feet from the front or rear of the school bus and shall not proceed until such school bus resumes motion, or until signaled by the school bus driver to proceed.
It is no defense to a charge under this division that the school bus involved failed to display or be equipped with an automatically extended stop warning sign as required by division (B) of this section.