This is a project that needs to be done. Logistically it looks to be a nightmare, but with a little careful planning, the process and end result look to be absolutely worth it...
Here you can see how Teacher Tom brought the scale down and did the project with preschoolers.
Teacher Tom took the scale down and used paint mixed with glue to achieve the correct consistency without breaking the bank. This project looks like it would use A LOT of paint which could get expensive very quick in a classroom. The other issue it could present might have to do with the sheer weight of the paint.
I am thinking of using several of the boxes I have laying around left over from all the deliveries after my birthday online shopping spree. I mostly bought books, so the boxes really are the perfect size and shape for something like this. This also looks like something you may want to do as an outside project.
I know my kids will get a kick out of it as well.