grammar - What is the name of this system of proof correction marks?

I remember in English classes when my teacher had used this sort of system when correcting essays in the class.

I never asked her about what it was and just complied and made the revisions to my essay according to the markings.

I'm quite interested in this subject now—I've illustrated a reference of it and linked to it below. Can anyone tell me the name of this system, and where can I learn more about it?

Answer

This paper (PDF) lists what it calls the "British standard institution proof correction marks". I can see your "Capitalise" mark on the list, but not the other two.

Merriam-Webster offers this list of proofreaders' marks.

Edit: Courtesy of Kosmonaut, here's a link to Proofreader’s and Editor’s Symbols over at University of Colorado. All three of your symbols are on that list.