I hate to say it but many educators feel this way and it just drives me crazy. YOU know what your son understands and doesn't. When my daughter was younger I allowed and encouraged her to take books from home with her to school so she didn't have to check out books at the school library without my guidance, since the school only allows the children to pick from a limited number of "grade level" books. Now that she's older she see the value in being picky about her reading material.
Your son's teacher might be pushing the lower leveled books to slow down his progression because it's very difficult to educate an outlier.
Junie B. Jones - ewwww. Gifted minds should read books by gifted writers. Encourage him to read the classics. His "experience" will grow with his imagination.
