How is this fair? Should I complain?

I am currently working as a teacher's aide and have finished my 3rd year of uni. Next year, I am given the opportunity to work as a classroom teacher. I will work alongside another teacher, and we will team teach. Now this teacher, I will call him Joe, is someone who I have already worked with this year. He is great with students but is bad at doing paperwork. Just for context, the school work at requires a lot of paperwork. Oftentimes, Joe has dumped stuff on me to complete for him. He would say things like, “you're not a snitch are you" and make me do some of his markings, writing annotated programs etc. Another coworker of mine observed this behaviour and complained to our boss who told him that he shouldn't ask me to do his work for him. When he first joined at the beginning of the year, Joe also informed me about how his teacher's aide in the past have not been entirely helpful. However, i am now starting to wonder whether his stories are even valid.

My concern is that since I'll be team teaching with him next year (him doing 2 subjects and me doing 3), he will still try to dump things on me to do. He has told me how he complained about the teacher he was team teaching with at his previous school because her attitude was not pleasant and she was spiteful when he occasionally asked her to cover his class. At our school, all staff members (we're a small group) have individual meetings with our boss at the end of the year, regarding issues or challenges we have faced. I am thinking of bringing up this concern. What are some things I should mention? And how should my attitude be towards Joe next year. Aside from this, he is an amazing and wonderful person, and I genuinely think he is really supportive. He is just extremely lazy with paperwork and I feel like he thinks he can just use me because I’m new and maybe too nice? I find it hard to say no when he asks me to do things. In the past, he has become quite short with me on days I have shown reluctance to do work for him.

Additionally, next year I will still be in uni full time and working full time so I’m really stressed about having to do his extra work.