I could be wrong, but I think he may have been in 31 General Reconnaissance School. He specifically mentions that he is training for flying boats. This description of the 31 General Reconnaissance school:
https://en.wikipedia.org/wiki/No._31_GRS_BCATP
mentions that "The school trained pilots and observers in the techniques of patrolling oceans using the Avro Anson."
The No. 32 Air Navigation School taught a four week course in astronavigation.