You go to Hogwart's to learn (or defeat evil, you can't have both...unless you're Hermione), you are given books for this purpose. As you go up in your school years you gain access to more and more powerful spells from classes and lessons.
I can imagine it's a struggle to keep up to speed on what spell is more powerful than the other, and that's not to mention all the spells not listed in any of your text books or mentioned in.
Is there then a codified list of all spells? A Magic-Wikia page? A Spell-Dewey decimal system? At the least a 'level' system?