Well... as a parent, I often act as a "tutor" for my kids. Mostly informally (although we did set up a more formal tutoring structure for my older kid's high school honor math years because it was daily/ongoing). And the more a parent performs that role, the more they understand exactly what is (and isn't) going on academically in the kid's classroom. Leading in many cases to more discussion with the school on assignments and curriculum (and teacher quality). I have a lot of education (masters degree), so I am probably more able to tutor effectively than many parents. And I only have 2 kids -- clearly the more kids you have, the harder this would be to fill this role.
