Mom, my name is Alexander

Alex has taken to being called by his full name, Alexander, since school has started. I feel bad as I think this is due to my mistake of putting his full name on all of his school paperwork when I was registering him last Spring. On the first day of school I noticed all his name tags stating Alexander instead of Alex. Since that first day I've been told by many people that Alex is now introducing himself as "Alexander" and I've also been corrected a few times by Mr. Alexander himself. His school work makes me laugh the most, however, as the "ander" part of his name looks like an after-thought, almost like a last name. I wonder how long this will last.