A parent's view
It is interesting to me that you posted this as I'm currently going through it as a parent. I'm not a teacher but am a curriculum developer. My son, who is seven, transferred to a new school in a new state this fall. In our previous school district, he would have been starting 2nd grade. When the principle reviewed his test schools and the fact that he was identified as highly gifted, she recommended that he be placed in third grade instead of second grade, in other words, that he should skip a grade. I should add that his previous school had a wonderful gifted program and this school district does not have one at all. He reads at a 4th grade level and does math at a 5th grade level. We placed him in 3rd grade. I had no doubt after our initial meeting with his teacher that she seriously did not approve of students skipping grades. She actually grimaced when she reviewed his file and pointed out that he had skipped a grade!
After just 5 days, she called me into a conference and told me that she was strongly recommending that Hunter be placed in 2nd grade, not because he couldn't do the academic work, but because she felt he wasn't emotionally or socially ready for 3rd grade. As you can imagine, I have VERY mixed feelings about this. I am under no illusions that my son is very much a 7 year old emotionally and socially. That is the challenge of parenting and teaching gifted children, trying to find a way to balance their academic, intellectual, social and emotional needs.
I was also very aware of the situation that I was in, politically. I knew that if I fought her on this, my son would suffer in her classroom. If I asked that he be placed in another 3rd grade class, this particular teacher was verbal enough to plant doubts/issues in the mind of his new teacher. I also knew that my son probably had some of the maturity issues that she mentioned. So I opted to place him in second grade with assurances that his academics would be enhance to address his special needs.
Now I'm dealing with the issue that the second grade teacher, who told me when my son transferred to her class that he would be given advanced work, does not have the time or resources to deal with any student's special needs. You can imagine the level of frustration I am feeling!
The bottle line is this: if you are going to recommend that a student skips a grade you HAVE to have all the parties' support, especially the new teacher's.
As far as not having classroom materials to address this student's needs, talk to her mom. If this parent flagged her child's special needs then in all likelihood she is doing so at home. Ask her to send books from home to school. And there are tons of worksheet and programs on the Net that could be used as enhancement. Develop some shoebox , folder, center activities, whatever, that could be used by her and other advanced students.
I hope the insights of a parent who is dealing with this has helped.