Posner is in love with Dakin. He watches and follows him. Dakin is aware and not interested. Posner is in part distraught, but also appears to enjoy the pain of unrequited love.
Posner is aware that Irwin is fascinated by Dakin too – because he notices him watching Dakin as well. He chooses to confide in Irwin about his crush. Irwin does not return the confidence. This shows Posner’s sneaky side – something which reoccurs when he is grown up and tries to get Irwin to say something on tape about liking Dakin.
Posner doesn’t fit in with the others. He is not accepted by Hector in the same way – he is never picked to ride on the bike, although abuse is no way a sign of approval. He attempts to find a role for himself as the dictionary boy. The fact that he doesn’t fit in seems directly linked to his eventual breakdown.
He gets a scholarship to Cambridge. It seems this is because of his answer on the Holocaust and his detachment, despite being Jewish. This exemplifies Irwin’s approach to getting the boys in, but also demonstrates the amoral or even immoral aspects of that approach.