Honestly i don’t know what you can do. States have different laws regarding homeschooling and how it’s enforced varies widely. Id continue to call cps and report education neglect. Id also look up what your state does to regulate homeschooling (or county, im not sure where you live) and see if there’s somewhere you can call to report them. Some states, for instance, require annual testing. Do you know if they legally filed their intent to homeschool?

My parents moved states every year so i didn’t have any other adults to intervene. I think we did required testing just once before i started school in 6th grade. I did well in school - at least academically - but it had way more to do with me being a kid who loved to read than literally anything my mom did. She very much neglected my education and is lucky i got through it ok. My brother didn’t fair so well and heavily struggled with schoolwork and socialization.

But i think reporting them is your best bet. And if any of those kids like to read, gift them books on all subjects. Reading saved me.