First of all, thanks SO much for all the supportive comments. It's so good to know there are people out there on my side!!

Secondly: I am SO on top of this Bad Bus situation! Monday afternoon, as soon as Mallory was feeling ok and resting a bit, I contacted the SIVOM. That's the parents' organisation that actually negotiates and signs the contract with the private transportation company. The office was closed, but I got an appointment right away for the next morning when it opened at nine am.

I told the representative the whole story and stated my main concerns:
A. The bus driver should not start the bus until everyone is sitting. That is a basic safety rule (and we all see why now, right?). Thanks to efforts by parents in the past, the bus driver has plenty of power to enforce this. If a child doesn't obey him, he can even take his/her bus pass away and leave mom or dad to drive the miscreant to school. It should NOT be left up to the younger kids (age 11) to try to make the older kids ( up to age 15!) act like decent people and move their bags off the seats.
B. There is apparently no SOP for medical emergencies. As Mallory sat clutching a wad of bloody kleenex to the back of her head, the bus driver drove into town (4km away) and hoped for the best. He had no clue what to do with her. He stopped the bus on the main road at the entrance to town and made all the kids get out, including Mallory. He walked with her to a seamstress' shop and peered through the window. He had a vague idea there was a nurses office somewhere nearby. There wasn't and I don't know what he would have done if she passed out. As it was, after much discussion (Alexa said it took AGES), one of the older kids said that there was a small medical clinic on the north edge of town. He then sent the other kids walking off to the junior high (even Alexa) and told Mallory to get back on the bus alone. She was weepy, starting to feel woozy, and beginning to feel like help might be long in coming- not a good feeling when you are 11 years old, bleeding from the head and alone with some strange guy who seems completely clueless.
He drove her to the clinic, walked her in, told the doctor to take her and left.
And get this: When the SIVOM representative phoned the transport company on Tuesday morning, she was told that the guy hadn't even mentioned the incident to anyone. What a responsible individual, eh? A real prince.

All of the above made me very worried about how such a person would handle a more serious emergency. The mind reels.
Luckily, the SIVOM representative agees and is talking to the SAT (the transport company) about outlining some emergency procedures for the drivers on school runs.

I'm also deep in the insurance stuff. I spent yesterday alternating calls between the SAT and my insurance company. I finally got sick of it and forced them to speak to each other. That seemed to do the trick. I found out this morning from the SAT that our own insurance will pay for Mallory's medical bills, but then will be reimbursed by the insurance of the SAT. The woman there also told me that the driver had just submitted a report of the incident.
I'd love to hear his version of the whole thing...