when did commander meet students?

I have been neglecting old events for quite some time and before reading a new summer event decided to catch up on school stories. So i started reading the first one (school of lock) and commander already seems familiar with both students and marciana. At the same time in the beggining they do explain what MMR schools is, so i know it should be the 1 event in the timeline. My question is - do we have an explanation how he knows all of them?