Elementary school? Is that the same as Primary School in the UK? Ages 4/5 - 10/11?
My kids go to bed at 7pm, and I get a lot of time to myself in the evening. My eldest now stays up until 8.30pm - he's 8 - but he has to spend the time quietly, reading, or writing, or doing something productive and/or creative.
We get up for school at 7am, and on 12 hours of sleep the kids are cheery, happy, alert, productive, inspired and eager. They can manage with less sleep, but I notice a difference in their behaviour. I'm strict about bedtime, because it's important. They've never been allowed to play for time, to ask for more stories, to eat or drink in the middle of the night, to come into my bed (unless ill) - they've got a lot of learning to do, and they can't do it properly if they've not had a good night's sleep.