To Kumon or Not to Kumon or "when public education is not enough"

I am writing this as I sit at Kumon waiting for my kids to finish their homework.  This isn't regular school homework; no, school is officially out today. And this isn't summer school homework either; my kids aren't at that age where summer school is necessary.  

And yet, I am here at a place which for all intents and purposes is like school, what with reading and math lessons followed by nightly homework.  Expect unlike summer school, this is a paid engagement; and the actual price depends on which Kumon you go to.

The reason I am subjecting both my kids and my wallet to this (according to them) abuse is the belief that they will excel further in school.  Although thanks to common core, what is taught here is not the same there and vica versa.  

Worse still, Kumon excels the student forward through complex stacking memorizing, whereby what is learned last time is added to incremently in future lessons.  It's similar to regular school but at an accelerated pace.  That wouldn't be bad if the school didn't then overwrite everything learned with their own lessons.

Sometimes I feel like I'm wasting my time and money but the progress I see from my children makes it worthwhile.  So that means I'll have to increase my diligence to make sure all their hard work in Kumon isn't wasted.  Which also means I have homework too.

Given this, I might ask myself what advantage does school offer?  That's pretty easy given the friendships and other life lessons learned.  Plus, my kids' school has science lab, art, and computer science (although many other schools don't).  But they are still limited in what a teacher can teach in a period and what an entire class of easily distracted children can learn. They still do teach and my children's district is one of the best in SoCal, so it wouldn't be terrible if we didn't do it. But we want the best for our kids and that includes giving them every opportunity to excel (regardless of the cost). And until I see differently, that will include reading and math lessons at a premium.