If he had expressed a keen interest in witnessing a church service, my response may be different. But he shouldn't go to mass out of convenience. You may have to get up a little earlier than usual the Sunday morning after the sleepover. I feel like we are engaged in battle. I encourage, push, prod, threaten and punish.
Nothing seems to work.
Your tuition pays for your son to have a full-time teacher whose job it is to assign homework and to make sure it gets done. If he is not getting his work done, that is between him and the teacher who assigned it. And there is no better way to teach this particular lesson than to send your son to school unprepared. If he is not taught now that he is responsible for doing his own work, the battle you currently are engaged in will turn into an all-out war when your son gets older. Meet with your son's teacher and describe in detail what goes on in your home when it comes to homework.