I love the fact that I feel as if I KNOW the Fire boy! He somehow looks just like a young student; his body JUST as that person would be sitting and he WOULD be showing off his fire. The angles, the perspective etc is all really challenging and impressive. In some ways this is more technically impressive than your Annikas, but the original Annika still has it! She just looks up at us and steps right into our heart- we want to hug her and share her journey with her!
The leather work is very good, as ever and the lighting is great.
To truly nitpick, I would say that the Fire boy's jawline is just a tad odd- I can't quite put my finger on it. If you wanted to push the realism a tiny fraction, things might look slightly less perfect. The stones could have a little dirt or cracks etc; however, you could argue that you wanted the Academy to look perfect if you wish. Might I suggest you make a female character with slightly more weight on her some time? Something more than an improbably 22" waist.
I'm hard pressed to decide between 4.5 and 5 again. Only looking at the very best of deviantArt reminds me that it might be possible to push yourself just a little further...