How do I get my kids to bed earlier?

My 4 and 2 year old do not fall asleep until sometimes 11pm. They both horribly fight bedtime. It starts at 8, when they get baths. And then we wind down with a book. But they’re always sooo energetic all day every day. They roll around in bed laughing and talking and sometimes screaming and crying for HOURS. I am so exhausted by it. My 4 year old is starting school soon and he has to be there at 9am and I just don’t know how to get him to bed earlier so he wakes up on time. I’ve tried wearing him out all day, letting him nap, starting routine earlier/later. Nothing is helping!