I am Chickenman
http://en.wikipedia.org/wiki/Aarne-Thompson_classification_system
Actually, there's more than 2500 categorized "plots" recognized as common to human psyche and seen in mythos worldwide.
2500 is more than 8.
Might want to inform your teacher that she's teaching you to be ignorant.
Might want to learn reading comprehension. Note, first of all, that the Aarne-Thompson classification system is specifically related to folklore, as opposed to all general fiction, and therefore gets quite specific. Note also that those 2500 plots are grouped into (if I've counted correctly) 43 less specific categories, which are in turn reduced to six general groups (6 is fewer than 8, if you needed a reminder), and it's an entirely different categorization system. It's like you've said that there can't be six kingdoms of life, 'cause there are millions of species. I mean seriously, 124 of those plots are jokes about priests.
OP: any list of plots which does not include the
bildungsroman is missing out on something. The system, though, isn't terrible, though I feel like it's missing some things - 4 is very poorly defined, first of all, and since
Romeo and Juliet is itself a classical tragedy and falls therefore under category 2 (Juliet is totally the tragic hero and not Romeo, btw), it could have been named much better. And in seriousness, the coming-of-age story is a very significant plot and deserves to be included. The Hero's Journey is a tricky one; its heroes aren't necessarily irrepressible, but I can't think of one off the top of my head that you can't arguably pick apart into kind of sort of falling under other categories.
The people who object to taxonomy of literature on the grounds that it is bad are being overdramatic and silly. The people who are arguing against the system on the grounds that stories shouldn't have just one plot are correct but irrelevant; the system is not reducing the entire story to one plot, merely classifying each plot within a story.
The people who object to taxonomy of literature on the grounds that it is pointless, however, are probably right.