Acutally, some school areas and after-school activities request the stepparents fill their names in the parents' spots because we're the first contact. Even though I have a power of attorney, I rarely have to use it. I've enrolled my stepchildren in their schools (usually the only one available to do so), activities, signed for them to get their shots (2 days ago), etc. One school district had a place for natural NCP on the back of the registration form. On the front, there were boxes in which stepparent was an option to check.
This new school district had ONE form that had a place to sign the name of birth father, birth mother and other adult in the home. I was told by the school that since I am the resident mother in our home to put my name in the area of mother/legal guardian (and the same with the other military/afterschool activities). So, on the form it states child lives with father and stepparent. According to their forms and policies, I'm lying if I state I'm the birth/natural mother. I went out of my way to ask and offer the biomom's names and numbers (although I usually have to find where they're living and telephone numbers) and create spaces. What I'm seeing is that that organizations want the first lines of contact and who is in the area to get to the child, then emergency contacts since there are so many blended families and out-of-area parents that just don't care.
I don't know how they process it in their computers. They have one form that specifies who the natural/birth parents are, and the stepparents are expected to be listed under any other parent line. I also don't have to try to be their mother as they know their moms. They have their own relationship, and we have our own. Maybe I would stress being a stepparent more if biomom didn't have to be tracked down or she showed enough interest to, at least, talk to her child.