Rachael Bouma calculated the cost of keeping rambunctious kindergartners under control at her son’s school at exactly $227.

That was the amount she and other parents in the Tacoma district figured every family with kids in Lowell Elementary’s kindergarten classes would need to contribute to save the jobs of three teacher’s aides. While some families gave more and some less, the parents ended up raising $16,000 in a few months, and all three classes got their aides.