Example article:
https://www.theguardian.com/lifeandstyle/2019/jun/20/is-brea...
You also have to consider that women are sometimes bullied into breastfeeding even when it's very hard for them and that is the author's main message. Otherwise she still thinks that "breast is best": "Breastfeeding seems to improve digestion in the first year, lowers rashes for infants and is especially important for preterm babies. It also seems likely that it has some impact on reducing ear infections in young children and lowers the risk of breast cancer for the mother."
"Breastfeeding in the 21st century: epidemiology, mechanisms, and lifelong effect" - https://www.thelancet.com/journals/lancet/article/PIIS0140-6...
Breastfeeding is one of many variables and formula has come a long way.
* it's study not studies
* it refers strictly to educational performance
* it's likely detecting something else entirely: "The researchers found that same-sex parents are often wealthier, older and more educated than the typical different-sex couple. Same-sex couples often have to use expensive fertility treatments to have a child, meaning they are very motivated to become parents and tend to have a high level of wealth. This is likely to be a key reason their children perform well in school, the economists found" [...] "When the economists controlled for income and wealth, there were a much smaller gap between the test scores of children of same-sex parents and children different-sex parents, although children of homosexual couples still had slightly higher scores."
A basic google query will get a ton of results. Here are a few.
Overview of 75 studies: https://whatweknow.inequality.cornell.edu/topics/lgbt-equali...
https://thinkprogress.org/same-sex-parenting-study-age-25-67...
https://qz.com/1320434/new-research-debunks-old-science-abou...
If you're making the effort of linking to studies that support a specific statement, please link to the actual studies and not opinion articles about them.
In any case, I would not expect kids with same sex parents to do worse in school or have noticeable psychological issues, which is what these studies were looking for - these are pretty heavy issues after all.
But I would expect that they are slightly worse for subtler reasons: maybe they're a bit more prone to infections in the first years because they weren't breast-fed, maybe they're distressed in school because they're being subtly bullied (mentioned in one article, btw) and so on. Remember that the original claim was "they're no worse", not that they're not much worse. I agree that they're probably not much worse, but a male-female couple has thousands and thousands of years of social support and nature on its side. Of course it's going to be in some ways better.
