Rule "Ji Shi" and life experiences

I remember in the first class were "Ji Shi" rule. All the walls were plastered with posters. The teacher held oral questioning how to write; warned: who can say that through the "s" - get a count. In general, all the conditions. So one girl still said that through the "s", got her number. And right behind it - the second.
I was outraged, worn around the house in circles, "how so? how could not remember and do not remove any lesson from the experience of the previous speaker? »
Now grown up a bit, I work in tech support. I remember those girls almost tenderly ...