I think it's useful to pass on your child's frustration with lack of progress to the teacher. Teachers at this level should be first and foremost focused on the affective domain of learning.
Two questions that have been effective for me to ask in situations like this:
*Is 28 his instructional level or his independent level? (As in, does he make errors at 28, and therefore needs instruction, or does he pass the test at 28? Teachers will use both numbers with parents without qualifying which is which.)
If 28 is independent:
*"How do you target his instruction so that he can continue to grow without finding his instructional level?" You might be surprised. A lot of teachers know what they're doing
If 28 is instructional:
*"I'm concerned at his lack of progress this year in reading. What needs to happen so he can continue to progress?" (28 and 38 tend to be barriers for kids. "Maturity" might be the answer and you just need to wait it out.)
I still honestly don't see a big difference between 28 and 34. However, since we've also had dreadful experiences with lack of instruction resulting from these reading level caps, you might also want to check on the type of instruction and the frequency. I would simply cast it as a question of "help me understand what this looks like to help me talk to my child at home."
