I couldn’t find any reference to clumped school grading like you describe, but I’d guess these teachers are reinventing [k-means clustering][1], badly. I’d expect to find a certain amount of subjectivity in actual practice, for example, even when a given tutorial implies it’s a rigorous method to assign grades. This is an NP-hard algorithm, so I wouldn’t expect to find a SQL implementation. There are many implementations in other programming languages better suited to the task linked at the bottom of that article. [1]: https://en.wikipedia.org/wiki/K-means_clustering