I have practically no experience since my son is only starting "real school" next year, but from what I've read the best thing to do with a gifted kid is try things out. If it was me I'd have her try the lunch with the older kids for a few weeks. Then if it works out you have a good argument for a grade skip and if not you can say its not working out and put her back with 1st grade lunch. If you explain it to her like that she might be willing to give it a try. If you don't try you really won't know if it would have been better or not. good luck =]