So, the thought has occurred to me that, perhaps, if I step up and act motherly together with DH in his plan to get the kids to do more schoolwork in order to bring up their grades (they are both failing Math), that BM might think I'm overstepping (or doing her job) and she'd step up and at least attempt to do HER job a little bit better.

I know from past experience that she thinks I'm not their mother and so have no right to be dealing with anything regarding their schooling. I looked up the kids' school websites for DH about a year ago, provided him direct links as well as teachers' contact info. He then contacted the teachers, arranged conferences, etc but he mentioned to BM that I found the websites and she flipped out on him, telling him that I am not allowed to be on those websites because I'm not the kids' mother. Well, I had a good laugh at her because those websites are PUBLIC, anyone can check them out; and it wasn't as though I was contacting the school, DH was doing all that, I was just helping him.

Anyway, the way I'd be involved is:
1. Helping DH make the worksheets for the kids to work on while at mum's (usually BM would not have to know I helped with anything, unless the kids tell her and I don't think they do out of fear of upsetting her)
2. Speaking to them on the phone when he calls to check up i.e. DH and I call together (the kids barely talk on the phone to DH and the one time I spoke to them on the phone, SS sounded scared out of his mind because, no doubt his mum was standing over him listening and he was worried about hurting her feelings)
3. Helping DH explain the problems that they don't understand, get wrong, etc, over the phone. (at our house, I do this, BM probably doesn't know, because again, I doubt the kids tell her, I think they're afraid)

Anyway, surely all of this will piss off BM, it makes her look bad, but is that enough to propel her to work with DH on this (instead of me) or work separately with the kids on her own?

Or will it just create more tension between everyone, which will simply hurt the kids too much??

Right now everything is fairly civil. I do not speak to BM at all, everything goes through DH, the only contact I have with BM is to wave to her and kids as they leave on Sunday evening. I do not speak to the kids at all during the week, DH does not even mention me (e.g. Stepmom31 said hi) when he does speak to them (not even if I'm the one who reminded him to call/text them). We have pretty much removed my existence as part of the kids' lives during the week in order to reassure BM that I'm not in this to take over her role as their mother, something she was tremendously concerned about.

The kids have said to me that they are willing to do extra work during the week, they don't want to be considered dumb or stupid, they used to get good grades before. Also, they consider me to be a very smart person, I am more educated than both their parents and have lived the life they dream of -> college, world travel, good job etc. all before settling down to start a family, (unlike their mum, who got pregnant, dropped out of school, never had a good job, hasn't traveled), so I know they look up to me. But I think it's something they admit only at dad's house and wouldn't dare whisper at mum's. They respect me, but they love their mom.

Anyway, it's all just a thought...