Save yourself years of fighting, headaches and bullshit. NOT MY KIDS NOT MY PROBLEM!!.....SAY IT AGAIN NOT MY KIDS NOT MY PROBLEM. Really it's thier grades, theri rooms as long as the mess does not spread to the rest of the house screw it. Tell them I don't care what your rooms look like the rest of the house MUST be kept cleam. Talk to YOUR daughter, explain to her what you expect from her and you are HER Mother and you don't concern yourself with how they behave. If you don't take this approach now you will sooner or later. There is alway the option uf RUNNING FOR THE HILLS NOW!!!!!!!!!!!!!!!!!!

Just read your bio. It seems that you and your SO have different parenting styles, and unfortunately all the children are at an age where they are not going to adapt well to some newbie marching in wanting to change the way the home is run. You and your daughter are used to doing things one way, he and his children have 6 years being used to doing it theirs.

You say your SO is 'with you' when it comes to rules on keeping things tidy and clean, but he is not. If you are doing most of the enforcement he is paying lip service to your ideas when he is with you, because he means well, but has no real inclination to implement them. His actions are speaking louder than his words. If they've all been muddling along together in a slightly slobbish fashion there is probably something of a battle of wills if you have moved in and now want everyone to live up to your domestic standards. What happened when you moved in with him? Have you sat down all together and discussed the compromises that are needed now you are all living together? So that everyone buys in to the changes? I think you may have made the classic stepparent mistake of marching in and hurling yourself into applying your values and standards, and then ending up puzzled and frustrated when there is resistance to changes that only you think are necessary.

On the subject of grades, I really would not concern yourself too much, not all children are academic, and anyway because of their age it is really up to their Dad to manage that side of things. Obviously you both want to communicate the message that trying at school is important, but you are going to be overstepping if you have only recently moved in and now want to have a say in how a 15 year old performs at school.

Moving in with him has tought you something useful, you now know he parents differently. You are NOT going to be able to change that, any more than he is going to be able to change you. There may be scope for compromise and a few basic household rules to make things easier, he and his children should certainly be prepared to adapt and understand that you and your daughter have a right to have your views respected in the home, but you have to decide if that is good enough for you, or if living with them is going to be too annoying and stressful.

I do think you are burying your head in the sand about how 'great' your relationship with this man is, if he is ready to call it quits, and so are you. You need to think about the realities of your life as a family and whether it will make you and your daughter happy.