I suggest reading
http://www.davis.k12.ut.us/cms/lib07/UT01001306/Centricity/Domain/73/Learning%20Distinctions%20Between%20High%20Achievers%20and%20Gifted.pdf particular page 11. High achievers, often those in honors classes, are very different from gifted students in learning styles and needs. A good school district will have separate programs for each. The pacing, depth, discussions, and atmosphere of these two classes should be different.
Why do gifted students sometimes seem average in middle and high school? In elementary school, they become used to putting in little to no work for top grades. When school becomes more difficult, they have no study skills, are unused to overcoming failure, and don't know how to work hard. High achievers, on the other hand, learned these skills and often excel more in the later grades and after college.