I don't think it's in poor taste after marriage. If re-marriage is not inappropriate, then caring step-parenting is not inappropriate. Think of the alternative? A Cinderella-style EVIL stepmother? I think the exes will soemtimes never agree, but it's the EX's sick issue if they don't want more adults loving and trying to help thier children make it to adulthood safely and successfully. It's pathetic when they choose to get angry over a step-parent who wants to care, help and be involved. Like they fear they're going to be replaced (a ridiculous fear) in their kids' hearts?

However, a good stepparemtn who cares about the kid will try to find a way to aprticipate without allowing the other parent to feel threatened. In my case, because my husband's ex seems to be threatened by every move I make, I've had to totally stay out of a lot of stuff. It's pathetic, but I have to find different ways to show I care. I show I care by not letting the kid's mother get too crazy if I can help it (at least not crazy about the things I can help)... I show I care by checking up on thie rhomework & grades behing the scenes, talking bout it with my husband, and finding ways to free up his time so he can spent it with them studying and talking about college & such rather than cooking & cleaning when they're with us. luckily, he's a good father, has always been the one more involved with the teachers & such, and her presence at those conferences really started when they divorced in some odd reaction to ... I don't know, trying to prove she's involved? Trying to ... whatever.

I dont' think there's a teacher, coach, principal, counselor... or even kid's friends' parent around who would find it in bad taste for a step to care, to show up, to support and try to help. The only time someone would comment or even care is if it somehow upsets the other parent adn the other parent makes an issue of it.

But if the other parent IS making an issue of it, the damage to the kids of the other parent being upset over this and gossipping, making everyone uncomfrotable, is more damaging than the failure of the step to be present at the parent-teacher conferences.... so the step should step out if the other parent is unable to handle things gracefully. THAT is the thing that will be the best result for this kid... in this situation. It's not a good situation, but that's the other parent they're stuck with... a crazy one who prefers to alienate caring adults from the child's life rather than welcome the help. It's not an optimal situation, but the poitn is to make the best of the bad situation, the step has to back off for that thing.

Now, sometimes, there are ways to get around it and not upset the other parent... setting up separate parent-teacher conferences is one common way of fixing that. Maybe you could try that?