I think A kinda realized that he could have developed romantic feeling for the teacher and pulled away, now he seems to be testing him.
I thought when he saw everyone with their family except him, he felt different and sad, jealous, then in his new school he made so many 'friends' for not to feel lonely because he was yearning for a family.
And I also think he idistancing himself form Jiri cuz he is jealous of him too.
he is distancing*
ohhh that's probably why !!
I think A kinda realized that he could have developed romantic feeling for the teacher and pulled away, now he seems to be testing him.