I'm reading this essay by John Taylor Gatto but couldn't understand the last sentence. Please help explain.
The third lesson I teach kids is indifference. I teach children not to care about anything too much, even though they want to make it appear that they do. How I do this is very subtle. I do it by demanding that they become totally involved in my lessons, jumping up and down in their seats with anticipation, competing vigorously with each other for my favor. It's heartwarming when they do that, it impresses everyone, even me. When I'm at my best I plan lessons very carefully in order to produce this show of enthusiasm. But when the bell rings I insist that they stop whatever it is that we've been working on and proceed quickly to the next work station. They must turn on and off like a light switch. Nothing important is ever finished in my class, nor in any other class I know of. Students never have a complete experience except on the installment plan.
What does this "installment plan" mean? Is it an analogy?