Apparently the best reason anybody has for not recognizing Pluto as a Kuiper Belt Object and not a major planet is "you’d upset the schoolchildren." This, as it is with conversion to the metric system, is an imaginary problem that will sort itself out within a generation (granted, with the metric system, you’ll probably have to replace some road signs earlier than you would otherwise). Take a look at the orbits: Pluto is far more elliptical in its orbit than the genuine major planets and more like a comet than a major planet in its inclination (here’s the inner planet orbits chart for comparison).
Your assignment: find a better mnemonic than "My very excellent mother just served us nachos" (in order to qualify as "better," it must have a substantially different structure).