(Original post by Speleo)
It's no secret that people with low intelligence are more likely to fail in school, but we're not stopping stupid people having kids.
Single parent children (well, daughters with single mothers) are also more likely to have sex earlier, to have unsafe sex, and to have teen pregnancies than children with both parents. It's not just school. But you have a point.
As to the whole 'should they be allowed to adopt' I think not.
It's clearly, ahem, not meant to be.
And using single parent families as an argument doesn't really hold weight. Studies have shown that a single parent family isn't the best environment to raise a child in - but what are you going to do? Take the kid away from its mother/father? Force the parents back together?
It's just how it turned out. You can't change it.
Adoption is different. Where there is adoption, there are choices. In situations with adoption, where the best possible environment can be ensured for the child, a heterosexual couple should be favoured over homosexual as tried and tested (plus, what if they're both barren? they have less chance than homosexuals of reproducing) for the same reasons as a wealthy couple should be favoured over a poor.
The best possible place for the child should be found, financially, socially - and a child with both sex parents is more likely to grow up socially and mentally better adjusted.
Where there are willing heterosexual adoption parents, gays should be overlooked. However, there is one area I am not sure of. The situation older children in foster care are in. Foster care can be fairly damaging (but not always), and a stable home with gay parents is probably better than at least some foster care situations.
I know a kid whose mother was in a same-sex relationship with another woman. He didn't seem too bothered, but then, he could still see his father. And there are the problems of role-models and - someone's probably already mentioned this. I won't go on.