Hi Lorraine,
I'm a type 1 quite recently diagnosed. When I was diagnosed by the hospital my bloods were in the 20's and I was in a very bad way, but 12.9 does sound quite high, but could just be a dodgy meter reading, I wouldn't test my bloods at a pharmacy. Whilst meter readings are very accurate I have been told they can sometimes be incorrect depending on how old the meter is and how often it is used.
My 8yr old daughter caught me testing my bloods, and wanted to have a go so I thought it wouldn't hurt (obviously with a fresh pin) - she came out 5.5 which is about as normal as normal can get. So your son's first level would concern me as it did you - you have done the right thing by informing the doctors. In my experience Doctors take these things "very" seriously and I was ordered to go the hospital straight away. I very much doubt they would let you go if they were worried. That said I would suggest you keep an eye on him and if you can do a few more blood tests at different times of the day that would hopefully give you more peace of mind, expect a slight fluctuations but if he gets into double figures again take him back.
In the meantime, just watch what him closely. Look for excessive thirst, signs of thrush (not pleasant but common), vision problems and sudden weight loss - these are the classic symptoms.
I have my fingers crossed for the little fella and I am sure he'll be fine..