My son was also diagnosed with an advanced bone age of 11 at the age of 7.  He has been to several doctors and they have all told me that in my sons case the bones in his hand all measure at different ages.  Because of this we have received so many opinions as to how advanced the bone age is.  At this point the last bone age was read at 10 and he is 9 yrs.  I don’t know if this could be the case with your child, but it might be worth checking out.  We still worry wondering what if they are wrong, but what can you do?  I hope this was helpful.