L.G.
My daughter went through this in kindergarten also. She was fine the first few days of school but then did not want to get on the bus. Fortunately, we had a great bus driver. Unfortunately, she had to literally peel a bawling 5-year-old off me and physically place her on the bus. But then she gave her a seat right behind her, and as someone else suggested, the bus driver gave her little jobs to do. Within a couple of days, no more problems getting her on the bus. She is almost 13 now and does not even remember the whole thing! I told her that's not fair, because I do, and it was torture watching her get on that bus kicking and screaming!
On another note, however, I would make certain there is nothing else going on. In her later elementary years, she started telling me some of the things that went on in the bus and at the bus stop. She was never in danger, but out of respect for her level of discomfort with the conversation and activity going on, I started driving her to school. It ended up being a really great thing having conversations during those transition times to and from school. I noticed she opened up more about her day when I picked her up than when she rode the bus.