Transportation provided by school not up to my standards, what are my rights?

My special needs 10 year old (physical and intellectual disabilities) is taking a 12 passenger van to and from school, which is provided by the district. I have several major concerns about the safety of the vehicle.
1. There is not adequate head support provided, the top of the vehicle seat back barely comes to ds' occipital bone, plus he has 2 brain malformations which make whip lash even more dangerous
2. The seat belts are very twisted, I've gotten on the van several times to try to untwist them, but they are so badly twisted I can't get them to lay flat
3. The shoulder belt does not retract. Ds is able to snug up the lap belt (it takes a bit of force since the belts are quite stiff) but since the belt does not retract properly it just hangs off his torso (the retractor is located on the floor behind the seat)
4. Ds uses an incognito in our vehicles, but he is unable to do the clips himself, and the drivers do not understand my concern so he's been going without a booster. He is very close to 5 stepping in this vehicle ( I can feel the top of his hip bones above the top of the lap belt) but when he comes home the seat belt is very loose since no one takes the time to make sure he is tightening it, I've tried a standard booster (so he doesn't have to deal with the clips) but without it being latched into place he tips over (latch is not available). I remind him everyday to sit back, and tighten his belt but he needs help from an adult, and sitting properly does not remedy the safety issues of the vehicle.
I plan to call the school and voice my concerns, but I'm wondering how much of a day I actually get. Do I have a right to "nicely demand" a different vehicle? I can drive him to school, but not home, however it's 30 mjnutes away and the expense of has is prohibitive. Plus, he enjoys riding in the school van, it provides him a chance to socialize and be a little independent. So I hate to take this away from him, so I'm hoping to work something out. Any thoughts or suggestions?

This is not my area of expertise, but in general, if the child has an IEP, it can (and should, where relevant) include information on school transportation. Once that is established, you have significant rights under Federal education law, notably the IDEA and its supporting regulations, to ensure that there is an appropriate transportation environment for your child.

There is an online FAQ on this topic from the US Dept of Education at:
http://idea.ed.gov/explore/view/p/,root,dynamic,QaCorner,12,

Although that document is a little technical/legalistic in some of its phrasing, you can see that there is a pretty strong stance here that transportation is an important component of ensuring that the student receives an "appropriate public education."

So I would not hesitate at all to bring this up with the school and push back hard -- in a polite and constructive way, of course.

The other thing that comes to mind is that, even irrespective of IEPs and special needs, some aspects of this vehicle are problematic. Ideally there should be head restraints in all positions. And seatbelts that don't retract and are so twisted as to be essentially non-functional could cause a vehicle to fail its annual safety inspection (in states that still have one).

Call your bus barn and talk to the supervisor for special needs. Then call your local safe kids or knowledge tech to see, if they can help educate the supervisor.

I taught the bus aids how to tighten the stars harness after I Google it. Then printed out a colorful picture with where to pull.