A doctor should never use tTg on re-test for dietary compliance as other autoimmune diseases can elevate tTg levels. These can include liver disease, Hashimoto's thyroid disease, and a number of others. The correct test to use for dietary compliance is the AGA IgA/AGA IgG or the newer, more sensitive one, the DGP. Of course, you are not in the US so I am not sure what tests are used in other countries but it would be the ones testing for gliadin antibodies in the blood.
I am like your son....I had classic Celiac and weighed around 95 pounds at time of diagnosis and was extremely anemic. You say he has grown in height and gained weight....is he still suffering symptoms? If his symptoms have abated and his height and weight are improving, then I doubt his tTg is still that high from gluten ingestion alone becasue he wouldn't be gaining weight or growing. Don't panic about the anemia because that can take a while to resolve, even in children. Everyone makes mistakes in the beginning and you really need to tighten up his diet and make sure he is not being cc'd BUT I suspect he may have another autoimmune problems, with a tTg that high. I have 4 autoimmune diseases so I know the drill.
I would highly suggest he have a full Celiac panel done and that he be screened for other AI diseases. Most of the testing, if not all, would be blood work. It took me a while to bring my tTg down into the low normal range after diagnosis because of all the other problems I had. Doctors annoy the hell out of me...they make this mistake all the time and then blame the patient by making them feel they are not compliant.
Take a deep breath and then ask for more complete testing!
Hey thanks for the reply could i ask what tests / diseases i shud ask to do as would be handy to ask them do it as i am not sure which tests they did other then his ttg and his anemia others where there but i had no understanding and not sure what lvls etc they where. he has another blood test in april and i am hoping it has came down as i am being watched at a very close eye and assumed im just posioning my son with gluten but since the xmas holidays his bowel movements have been normal so im doing food diarys and when he goes bk to school if his bowels change i shall be very concerned as the school are saying theyr following a strict diet sure find out when he starts eating there again