a) The deputy head, Mrs Weller, only had one lung. This was proven by her never shouting at anyone.
b) Miss Frisby was a man. This was proven by her having a man's voice and a mostly male body. Genuinely very difficult for a child to know which she was.
c) Miss Blackstock and Mr Something-or-other were shagging. This was proven by her becoming pregnant and not being married.
now you go