To the OP: when my kids were your kids' ages, I did the same. When I had them I knew that I'd have to make sacrifices so that they could be healthy physically and emotionally. So we put their needs ahead of ours. People used to say we were mean, crazy, strict, controlling, blahblahblah. BUT, my kids, when awake, were generally not tantruming and whining. They were cheerful and pleasant. Besides, at night, in the summer, when it's dark, I want to have an adult conversation at a party. Not watch my two year old trying to navigate the porch steps for the 100th time in the dark!
We're pretty flexible NOW about sleep, but when they were little I was pretty strict. My kids are very good unless they're tired. In fact, I've always said that if you can't behave you must be tired. GO TO BED!!
As a teacher, I've seen the effects of liberal bed times. In fact, DS's first grade teacher said she wished MORE parents would keep their kids home when they're too tired to function. We sometimes plan in a rest day for DS.
There's a LOT of research about how sleep effects children, and how much sleep kids need.
http://www.newswise.com/articles/view/522402/?sc=rsmn
For a good nights rest, the National Sleep Foundation recommends children in elementary school sleep between 10 and 12 hours each night, and for teens to get about 8 1⁄2 to 9 hours of sleep.
However, Hoban says, the sleep children and teens actually get each night fall short of those recommendations, and many suffer from chronic sleep deprivation. And that lack of sleep is not only preventing them from being alert and ready to learn at school, but also from leading a healthy life.
A good night's sleep is important to a child's health and safety, notes Hoban. Children and teens who are dealing with chronic sleep deprivation have difficulty learning and paying attention in school, and some research also suggests theyre more likely to be overweight.