My daughter's teacher recommended another year of kindergarten to help her mature, but her twin brother is ready to move up.

I'm a dad of 3 and my older two are twins. Despite being womb mates these kids are so different from each other and are in separate classrooms.They have a September birthday in a December 31st cutoff state/district and turned 5 the day before school started. We knew they were on the young side for their grade but with a late cutoff we figured it made sense to send them. Neither are the youngest in their class and their preschool teacher recommended moving them up. Our son was an easy decision. Our daughter was harder but her teacher thought she would benefit from kindergarten.We are in January now and had a meeting with our daughter's teacher last week. She is concerned about her emotional maturity and social skills. My daughter is more of a wallflower and has a hard time getting involved and communicating with the other kids. One of the students mentioned that they have to be nice to my daughter because she is a little girl and they were big girls. The girl who said this is actually younger than my daughter but the teacher was concerned that the students see her as someone younger rather than as a peer. She wants our daughter to repeat the grade for another year of growth. She thinks it'll help with maturity, confidence, and leadership.The problem is that my son is killing it in kindergarten. His teacher raves about him and I don't want to hold him back just because of his sister. He is a friendly kid and already has made a bunch of friends in his class. I wouldn't keep him from them by allowing them to move on while he stays behind.My daughter is ahead academically and we are going to be getting her tested for ASD (high functioning). We have heard that autism can present differently in girls. Regardless of that, we need advice on how to handle this. If we hold her back while her brother moves forward I don't want her to resent me for life but I also don't want her to keep moving forward if she isn't ready. We have a few months before we have to make a decision but I have no clue what we will do at this point. via /r/Parenting http://bit.ly/2Uug1Pe