Startup Idea : Grade Time

For teachers: Teaching faculty spend a great amount of time grading papers and writing (or typing) comments about students' work to help them improve. Many times the comments fall in general categories and are repeated over and over when grading for an entire class. For example, you need more details here, Confusing choice of words, I like this section, part, answer. etc. Teachers could use a way to save time writing the same thing on multiple papers. This is what I propose for teachers at all levels. An app or utility that can hover over assignments submitted online that stores commonly used feedback phrases (in the instructor's own words or style) that can be selected and inserted on the students paper as text or handwriting. The teacher would enter the 20 or so comments in the app and as he/she reads the paper taps the appropriate comment and it is inserted (above, beside or in the margin) of the student's assignment. I know very little about software development but this seems like something that could be designed rather easily. There are also countless extensions that could serve other redundant professional tasks. Would love to hear your thoughts.