The wifi provides an opportunity for someone outside of the home to "babysit" the kids. In can provide improvement at the margin, if managed well.

Also, people have greed that can be exploited. If you want to continue your (admirable!) effort you can offer a different bribe.

Another point to note is that if the kid got halfway through the chapter on exponents, he's doing pretty well! Failure at math education means years behind, not weeks behind.