meal time after BCT
John - your son will be a lot more relaxed at meals after BCT. Since he's an IC, he will eat meals at a team table rather than with his squadron. If he's losing too much weight during BCT, they'll generally provide him with a supplement (like Ensure or Boost). You might mention that in a letter - the coaches may be able to help facilitate it if it's a real issue.
Our son's first letter home indicated that his teeth hurt too much to eat due to spending the day (and probably night) with his jaw clenched. However, he drank a ton of Boost or Ensure and actually ended up gaining weight during BCT.
As for your original question - my son says that going from BCT to the first school year was like attending a different place; after recognition, the changes were again so great, it was again like attending a different school; second year, same, etc.