Where and when was the worse fatal school bus accident in the U.S.

A very bad accident happened in Congers, NY back in the early 70's at a railroad crossing but I am not sure if it was the worst or most fatal one.

Train-School Bus Collision: Congers, New York
Time and Date: 7:55 a.m., March 24, 1972
Weather conditions: Clear.
Event: School bus driver failed to stop at a grade crossing, school bus struck by a slow moving freight train.
Injuries: Five male passengers of the school bus, ages 14 to 18, die, 44 students and driver injured.
Accident report: National Transportation Safety Board, Report Number; NTSB-RHR-73-1
Description of collision: At about 7:55 a.m., on Friday, March 24, 1972, an eastbound school bus was driven across a grade crossing on Gilchrist Road near Congers, N.Y., and was struck by the lead locomotive of a northbound Penn Central freight train. The train was traveling at an estimated speed of 25 m.p.h.; the posted track speed was 40 m.p.h.

Except for a stop sign, at which the bus driver failed to stop, and a standard railroad-crossing sign, the crossing was not specially protected. A student on board the bus reported first seeing the approaching train at about 600 feet west of the crossing; the train crew said they first saw the eastbound school bus when they were about 500 feet south of the crossing. At about 220 feet from the crossing the school bus momentarily declerated, but then resumed its initial speed. Meanwhile, the train crew applied emergency brakes at about 150 feet south of the crossing, way to late to bring the 4,230 ton freight train to a halt before impact. After the accident tiremarks were found at the grade crossing. Right tire marks started about 13 feet 5 inches west of the rail.
After impact the school bus was pushed 1,116 feet down the track by the train, and the body structure of the bus disintegrated. The rear section of the bus was torn loose, fell beside the track and overturned with a number of students underneath. Two of the several students who were ejected from the remaining portion of the bus passed through separated floor sections and fell between the rails into the path of the train.
As a result of the accident five students died. The bus driver and all 44 remaining students were injured. None of the train crew was injured. The driver, a 37-year-old male, was subsequently charged and convicted of five counts of criminal negligence as a result of this accident.

Cause of accident: The National Transportation Safety Board determined that the cause of this accident was the failure of the school bus driver to stop at the stop sign until the crossing was clear of railroad traffic. Contributing to the accident was the unnecessary routing of the school bus over a not specially protected railroad/highway grade crossing. The NTSB issued seven formal safety recommendations as a result of the accident.

Contributory factors: In its official report, the NTSB noted five specific highway safety recommendations. They are: (1) the lack of structural integrity of the body of the school bus, (2) the absence of highback padded seats and an occupant-restraint system in the school bus, (3) the presence of standing students in the bus, and (4) the action of the coupler of the lead locomotive, which caused the crash forces to be concentrated on the bus.

It was in Prestonsburg, Ky. Feb. 28, 1958, 27 children and the bus driver was killed

Definitely not the worst in history but here is a story about a bus accident that left one dead - http://newyorkcityaccidentlawyer.visionsmartnews.com/new-york-city-accident-lawyer-news_2002.html

I was in 9th grade when that accident happened. Several students lost limbs and yes a few there lives it was horrible. But there was another factor not mentioned about the famed "Ghilcrest Crossing" accident. The crossing was overgrown with large trees making visibilty in either direction difficult all the time. Shortly after the diaster the Towns residents took it upon themselves to take the trees down. I know I was there with my Father, working.