On school nights a 7 year old child should be in bed by at least 7:00 PM to 8:00 PM so that the child has enough time to get enough sleep before waking up in the morning.
When I was 7 years old my bed time was always 7:00 PM which meant I had to have my bath, get dressed and then be in bed by 7:00 PM.
That doesn't mean I was always asleep by 7:00 PM but I was always in my Pajamas and in bed by 7:00 PM because if I didn't I would get a spanking.
But as long as your 7 year old is getting at least 8 to 10 hours of sleep they are doing okay but I would not let a 7 year old stay up any later than 8:00 PM.