I think you have a worthwhile cause there. However, I already have some causes of my own that are taking up the left over time I have.
To be very honest, having worked in the school system for many years, I think the best approach would be for parents to get together and get with the appropriate administrators to address this issue. Politeness with persistance can work wonders.
However, if the school/s have parents that are highly neglectful of their children, boy will you have a battle on your hands, maybe not one you can win. Schools are often being asked to do what only the parents can realistically do.
My approach would be to arm the children with some kind of spray bottle antiseptic (don't too much trust those little sanitizer bottles they sell at the grocery stores etc.). Maybe something with
Colloidal Silver in it, maybe with some aroma therapy in it (they also can be anti bacterial.)
Maybe lavender and/or rose for any girl & something like peppermint for any boys. Of course boys would be laughed at if they had any "feminine" scents with them. Girls, tho, would probably get admiration for using the sweeter smelling fragrances.
If you decide to use the spray bottles, teach the children to not spray it around to a distracting extent. Even talk to the teacher/s in advance and ask how your children can do this w/o causing any distractions. She will probably appreciate the consideration as well as the hygeiene.
A child can be taught to not actually sit on the toilet seat when going to the potty. In addition, I personally don't use the first piece of toilet paper, but tear off at about 2 sheets the end & discard it in the toilet.
I would also pack their lunches, not have them eat the cafeteria food if the children are handling some of the same foods & utensils, which no doubt is happening. (Of course teach the children to be tactful in their avoidance of such things so the other kids don't get the feeling your kids think they have "cooties." Lol.)
If you kill beaucoup
parasites in your family & go on an ongoing maintainence project, you will at the very least decrease the infestation.
I am sorry you have not yet found what to do about the smaller children. Maybe someone on here will have an idea. My thought would be just to decrease the amount of the paracides based on body weight. But...resesarch might tell another story. I do know people have used zappers on their children & pets with good results, reportedly.
Oh, and by alllll means, please teach your children to not put their fingers, pencils, etc. into their mouths! This is a verrry hard habit to break, but it can be done with loving patience where they know, which I am sure is quite true, that you just want them to be healthy. (You gotta be sure you don't do that yourself at all. Maybe you can all work on it together as a kind of a game.)
Hope that helps any!