I would look into being appointed as her Lawful Guardian...

DH needs to do this I think in court?

On Mars works differently, SO appointed me as Aergia's guardian years ago cause he had sole custody and work out of town, this meant that I could make any decisions regarding her, school,medical without even contacting BM in his absence...

stupid BM and Aergia knows this lol and it's still not changed, if I was the Evil SM they make me out to be.. I can cause so much problems for BM, cause Aergia moved in with her about 2 months ago... they just better hope and pray SO lives till the day she's 21... or they will have no alternative to deal with me regarding money etc }:)

Look into getting a power of attorney. I don't know how much it will help but it does allow you to make medical decisions for both parents are unable to be reached. I know if it's prolonged it can help with school to just don't know to what effect.

My parents had to do it every year for.me and my sister when we were little and they were military incase they both were ever pulled for something.

Personally, I have never had a problem with the school or doctors. I think they just assume that I'm mom because I'm setting the appointments and paying. I even have a different last name.

One year, my name was accidentally taken off the pick up list. I asked for the school principal to come out and vouch for me (many many conferences were had by just me with the principal because of SS's behavior, so I knew he knew me). He said, yeah she can take them. She's their mother.

I know there were many times that my Parents would take my BS on vacation. My BM always had me sign a form giving her permission to make medical decision or seek medical care for BS in the event he needed it. I am sure there is a POA or some legal form your DH can sign giving you the ability to make medical decisions in his absence.

I've never been refused at a school or doctors office when dealing with skids. The only time they stopped me was when SD needed to go have her teeth capped. They were going to put her under at the hospital to do it. They told me only DH could sign those papers. BM couldn't even sign them. It had to be DH because he had sole custody.

I believe that your DH can grant you en loco parentis rights to act as your Skids parent on DH's behalf with a simple letter. Talk to your attorney.

I never needed one and never got one from my wife. I engaged medical care, signed school documents, attended Parent-Teacher conferences, and pretty much did whatever I wanted whenever I wanted to do it as far as acting in SS's best interests as his dad. Living in a conservative county in Texas has its advantages. No one ever questioned that I was his dad.

No one every told me I couldn't and if they had... it would not have much mattered and likely would have been nothing that our attorney could not readily deal with. Not even a Judge ever interfered with me acting as SS-24's dad.... since that is exactly what I have always been since before he turned 2yo.

My step son and I have the same last name, and my bological daughter has a different last name. I actually have MORE problems with getting things done for my daughter now that she has started school than with my step son because of the last names. 

Personally, though, we have a power of attorney that states that I can make decisions for medical and school. The school knows our situation and they know that his mother isn't truly involved and isn't sound enough to make those decisions, they allow me with no problem. His father signs his documents for all of his enrollment and such, other than that i fill everything out and take care of everything. His dad actually prefers this because he hates paperwork, and he absolutly hates dealing with people, even thought he is the most outgoing man in the world. lol. 

Thats what we use for the power of attorney. Some states require a notarypublic, some dont. Having it is ALWAYS better for legality and making sure they take it, though.