I am by no means an expert here, but I have a 7 and 10 yr old, am divorced and remarried, so I have a lot of experience with the step dad issues, as well as birth father issues that can come up.
Your son's behavior is not acceptable. Are you able to talk to his father about setting mutual rules? Rules that are expected to be followed in both households. Simple ones, like clean up after yourself, be respectful to your elders, do as you are told. My ex and I can barely pass in the same hallway, but we were able to sit down together and discuss some rules that are just non-negotiable. I certainly don't want my kids going to school and treating their teachers that way, and I doubt their father does either. Kids need to understand that there are reasons for a lot of the rules that are being set. The rules that weren't worth arguing about with bio-dad, like bedtimes or how much time is spent on electronics are ones that we sat down and explained to the boys, there are different rules here from there, and when you walk through the door here you better be prepared. We then stressed that no matter where you are, you are expected to remember your manners, be respectful, not be a slob, etc.
Your boyfriend may be getting into the equation a little late in the game. I understand that it is his home too, and he feels he has a right to contribute to the rules, etc., however think about it from your son's point of view. This guy comes in, and just takes over, calling him down (lazy, whether he is or not, is still name calling.), declaring how things should be done and what do you suppose his first thought is? You are not my dad, who are you do tell me what to do? Facts are facts, he's not his dad. What right does he truly have to get involved (from the mind of a child)? DH and I have been together for 7 years, I left my kids birth father when I was 3 months pregnant with my youngest and started dating DH when my youngest was a new born. Even at that, my oldest remembers life before, and it took many years for he and DH to come to terms with who each one was and what their roles are. Now, after 7 years, I wouldn't dream of handing a real punishment (things like grounding) without sitting down with DH, discussing it, and making sure that my son understands it was a mutual decision. But it took 7 years to get there. I think your boyfriend needs to butt out of the arguments and actually get to know the kid before he starts pushing his weight around. I would insist your son be respectful of him, but your boyfriend needs to respect his place as well.
Re: Hey, looky what I found!
Sara, Friend?
glove slap. I don't take crap.