I am not sure this has anything to do with same sex couples. This is more about economics and environment. A child out of financial difficulty has a better chance of success in life regardless of the sexual orientation of the parents.

He better be tall and have a good job. And drive a cool car.

I'm sorry, there are certain sacrifices I will not make for a child's education.

I suspect that these findings are due, at least in part, to the fact that most same-sex couples go to great lengths to have children (e.g., surrogacy or adoption), so they are eager to be parents and are on average more engaged in their kids' daily activities and more directly involved in their kids' education. But at least this helps shut down the baseless anti-gay "children need a mother and a father to thrive" argument.