This are 2 websites where they have different normal TSH, T3 and T4 for different ages (3 groups of children)
http://www.childrensmemorial.org/cme/online/article.asp?articleID=72
http://cat.inist.fr/?aModele=afficheN&cpsidt=13391788
0.3-3.0 is for adults (new range) , I know that TSH of children are higher,in the lab I took my analyses they have different TSH for different ages, 6.3 for an adult is high in any lab.About children may be it changed too. Better ask in the pediatric ENDO forum.
They have changed it from .3-3.0 now for ideal ... when I was 6.3 they considered me Hypo still (according to Mayo clinic here in minnesota) but not sure about everything else.... good luck
In the lab where I have tested my TSH:
Children with ages between 6 months - 16 years normal range for TSH is 0.5 - 6.5.
what is normal level of TSH ?