I think you have to either go for a full skip or subject acceleration. I don't think it would work to do a few days at one level. If nothing else it would confuse their testing regime. How about pushing for going to the next grade for her strongest subject and take it from there? If you have two sets of twins coming along you might as well get some of the fighting out of the way now. We don't use any of those tests here (NZ) or have gifted programmes for that matter so I can't comment on the marks but if you get her tested will the schools pay attention to the results?
