There are lots of posts about alphabetical codes-
I am assuming you are talking about VR here, a good place to start is the IPS Methods and Techniques book as it breaks down these codes. I have a pdf with a breakdown of these and if you are interested send me a pm and I can email it to you. Its not as good as the book but it gives you an idea what these codes are.
Regarding scores for younger kids I wouldnt personally get too hung on these at the moment, its not that many points they get. I think 4 is the maximum points the younger ones get.