The children know school math. And their blackboard is declarative and not imperative. Why would you suddenly introduce implicit state? i=i+1 is just confusing

The children know school math. And their blackboard is declarative and not imperative. Why would you suddenly introduce implicit state? i=i+1 is just confusing without a good and formal introduction. And once you have that introduction, your most of the way to modelling state in a functional declarative computing model.