I agree that parental involvement is critical, but success also depends on the school system. We moved when my oldest started kindergarten, and then 2 more times since then. The first of those two moves came in the middle of 1st grade, shortly after 9.11.01, and was a move into one of the best school districts in our new home state (or so we thought, after advice from sources who should have known). Academically, yes they were excellent, but socially it was a big mistake. By the time we left there, following her 5th grade year, she had a diagnosis of ADHD and ODD (Oppositional Difiant Disorder), which the school used to blame her for a situation out of her control. She was verbally bullied, and eventually fought back physically - in their words she had poor impulse control. When her 3rd grade teacher suggested she be evaluated, we did so - the school wouldn't because she was performing at grade level (as an average student), and didn't want to spend any money they didn't need to.
Fast forward to our current school district, which not only is better about dealing with bullying, but is all-around better about special-ed issues. She no longer has a 504 plan (never had an IEP since she performed at grade level), and is in fact one of the top students in her class (and had the top scores on the SAT which she took to qualify for the Center for Talented Youth).
Both school districts are in affluent areas - the first was probably MORE affluent - but had very different ideas about special-ed spending. The current school system has learned the every penny spent NOW to help these children means fewer dollars spent later. Maybe those dollars would end up being spent by another district, but maybe not. Barring moves because of a change in employment, families who are happy with the schools here are not likely to move. I guess maybe those districts that are pinching pennies also think they're saving because those families will be forced to move to another district to get the help they need.
OP - good luck, and I hope you get an acceptable outcome. Those children deserve to have either an aid on your bus, or alternate transportation. Some children don't do well on regular school busses, including some who don't have special needs.