Cute story. Corg and Dee sound like soul mates in many ways even for two of such a young age as found here. Enjoyed the recess play scenario.
Some proofreading may be needed:
In the sentence/paragraph..."Nobody ever worked with him anymore, not since last year when went from being the class weakling to the odd, shifty-eyed athlete in literally a couple of days."
(Note: The word "he" possibly needed between words "when" and "went".).
In the paragraph.. "The two locked fingers and Dee soon pulled up a chair and sat next to Corg. The spent the next twenty minutes working on the percentage problems that Mrs. Kemmerley had placed on the telescreen. Although Dee didn’t really get the mathematics behind percentages when they started the first problem, by the time they were on the third, she was doing most of the calculations by herself, not to mention the writing. They finished about fifteen minutes before recess."
(Note: In the second sentence "the spent" might possibly sound clearer as "they spent".)