As far as the author goes doing her teenage relationships, this is by far a more reliable outcome of the main character's education. For instance, he's had a lot more interaction with his school rival, more so than he has with the wallflower character. In point of fact, most teenage males tease and belittle the object of their desire, (which is a point in the favour of the MC/SR relationship) and these two are always "at each other's throats". Seeing the chemistry between them as the MC is placed into the rival house of the SR, it has become rather clear to those in the know (MC/SR shippers) that if they were in the same house - for instance if the MC had not argued with the sorting process - then this would have eventually evolved into a relationship or some description of courting process, as the SR is practically nobility and portrayed as such.
As a small touch and go explanation, not covering everything but what stands out to mind:
Flying lessons: 'Buck and Doe syndrome', ie showing off for the object of your affection. Both of which do so to differing extremes.
Midnight duel: SR trying to evaluate if the MC was able to take care of himself.
Duelling Club: Both are trying to show off that they've learnt more since the first attempt at a duel. SR shows him his snake and the MC shows off his prowess with handling said snake. Frankly, twelve years old is a tad TOO EARLY to be dealing with this sort of innuendo.
The MC didn't seem very keen on saving the rampant magical creature after it slashed up the SR.
The MC and SR have a small stand off where the SR attempts to curse him behind his back, after his misguided attempt to persuade the MC to drop out of the tournament ("I don't think you'll last ten minutes" in which a lot goes unsaid because the MC cuts him off).
The SR joins an extra curricular group designed to keep the MC and the rest of the school in check. The run-ins between the two with the SR trying to catch out the MC and does at one point, physically man handling him.
The MC pities the SR for his lot in life and tries to prevent him from doing something he'd regret (like murdering the Kindly Old Man/Manipulative Headmaster, depending on your fancy).
SR was unwilling to identify the MC as he would have been killed.
MC didn't have to, but he saved the SR's life in the "mysterious fire".
MC and SR are strangely respectful and nod to each other in the Epilogue.
It's an apple. It's incapable of feeling. Emotional or physical. What are you... high? (O_o)