Could it be a respiratory flare-up? My daughter eats less when she is starting to get sick. As a former teacher, I can tell you that sometimes lunch period does not provide a quality eating experience. How much time is given? Sometimes, by the time the children sit down to eat they have about 5-10 minutes to clear their plates. Who supervises? Although it was my break time, I always ate with my class to ensure that they atually ate. Otherwise, sometimes it's a play period. Perhaps you can ask to observe a lunch period.
My daughter is much younger than yours, but she also is a poor eater. Our CF team encouraged a g-tube for a long time before I finally accepted it. What made me finally change my mind was when our pulmonologist explained, "You would never think of denying your daughter treatment for a serious respiratory issue." "Well, the g-tube is the treatment she needs for this nutritional issue." Also, she showed us how important good nutrition is for improved lung function. She has had the g-tube for about six months. She has gone from 6% to 35% on the growth charts. She is stronger, healthier, and I think, happier. I am also reassured that she now has extra calories to handle those respiratory flare-ups. Hope this helps.
Maria (mother of three daughters, the youngest, Samantha w/cf)