The details are a bit vague. I can’t remember whether this was in class or if I was being shown the type of things that class was doing and asked if I’d like to join them. Either way, I clearly remember learning the function of parentheses in a mathematical expression.
When I moved to the junior school, I think I might have had different teachers for different subjects. I can only remember one teacher but I know I had other teachers too. As I was there for less than a year, it couldn’t be a case of having different teachers in different years. The teacher I remember used the “carrot” approach – she gave sweets to those of us who did well Something like “Quality Street” I think.