Wow! That's not so great. I really don't understand why they would make her do the 3rd grade work if they realize she is that advanced as to warrant 6th grade work. Duh.
Unfortunately I've heard that before.
Have you asked them to excuse her from 3rd grade work? I'm not sure how they could not especially since they are providing the 6th grade curriculum so they must be convinced she is proficient in 3rd.
I think you have to have the director make this decision, sometimes the grade level teacher doesn't get it.
If they are just trying to cover their bases, ask them to administer a 4th grade achievement test like IBTS or CAT when she starts school.
Maybe they will excuse her if you offer to sign a waiver releasing them of all liability if your daughter becomes a juvenile delinquent because she didn't do enough 4th grade worksheets?
One idea is to try and contact the director now, about this. Most administrators are accessible in the summer and they sure are a whole lot less busy!
Thats all I can come up with right now. Hope it's helpful.