Maybe you could come to an understanding that if you start 5 days early you will end your contract 5 days early or at the very least on the last day of school with the regular teacher contracts, (if you have a week extension).
And we all choose our professions. I too have left teaching but still have some things I do because it's expected at my current gig. So does my spouse. For example, I might not check email on Saturday but Sunday evening I will spend 30 minutes getting my week in order because if I don't, Monday ends up much more chaotic then it needs to be. All salaried employees do it. But I'm not cut out for manual labor at my age so I make it work. Just not an extra 30 hours per week any more.