Sometimes teachers will collaborate with teachers in other rooms or grades to make reading groups. I encourage you to make an appointment to talk to the teacher, stress you much your child likes her, share your concerns, and tell her the story about how much he got out of doing reading with child x,y and z, and ask her if she can sent up a collaboration with one of x,y or z's teachers.
I feel that a child does have an obligation to themself, to work at his or her readiness level at least 10 minutes 5 days a week. If you can't motivate your child to push themselves, then I believe you have to push them. This may seem mean, but compared to gradeskipping a child who is happy where they are socially, but 'HAS' to be gradeskipped because they are becoming ingrained underachievers, it's doesn't seem mean to me. This happened at our house, so I can see both sides. DS was insistant that he wasn't going to do a speck of work more than what the teachers asked for in 5th grade - so he HAD to skip. I think that if I had started him earlier with 'of course, this is what we do in our family, everyone works at their challeng level every day, just like eating vegtables' then we would have had many more options. I think...
smiles,
Grinity