i've never had a time i had to go to sleep and i never was late for school or any thing. In fact my dad is a construction worker and he would have me put his clothes in the dryer. Or have me stay up and empty/fill the ice trays. So he would have enough ice to keep his water cool all day in the hot sun, so he could have something to drink while working.
read the section of this article that says 7-12 years old. work backwards by figuring out what time you wake up in the morning, then count the amount of hours you need backwards and that will be your bedtime!!