How do I get my child out of school?

So I’ve got tickets to a football match for my sons Birthday but we need to leave early to make it and he’s at school until 15:00. I really want to leave at 14:00 to allow us enough time to get there and have a walk around and soak up the prematch atmosphere. We could make it if he came out on time but it’s normally 15:25-15:30 by the time they come out and then the school traffic would set us back and we would miss part of the game. I’ve been told you need a doctors note or letter to prove any appointments and I’m at a loose end. I also don’t want to give him a day off and lead him to believe that it’s okay to bunk off because my parents let me that one time. Any help is much appreciated!

I will just take the day off with him and make a day of it. Thanks for all the replies!