How do you handle gaming on school nights?

My 10 year old has been begging to play Minecraft with his friends after school. I want him to have social time but I'm worried about homework not getting done and bedtime slipping. Right now I'm saying weekends only but he thinks that's totally unfair. Other kids get to play during the week apparently. What's reasonable here? Should I set it up as a reward system or just keep the hard line?