Firstly, I do not believe this to be a duplicate of the related recently posted question due to the key fact that that user was anonymous to his class and I am not.
This has happened 3 times now. While taking standardized tests, someone cheats. These aren't just classroom tests, but rather officially proctored, nation-wide tests. The first time, some students had significantly more time, both starting before the official call to start, and ending after the official end. The Proctor was pretty relaxed, and either didn't notice / didn't care. The second time, someone's phone went off twice, and on full volume (the student in question had to stand up and manually turn the phone off). The Proctor did not alert his superiors, although many students had lost a significant amount of time and the incident negatively impacted our scores. We were told beforehand that any distractions during would be an immediate invalidation of the test (we even had to keep our phones in a box), but this seemed to go unnoticed. The third time was similar.
I complained to my peers afterward, and they all told me not to tell anyone or do anything for fear that it would cancel or negatively impact our scores (most of them did well). I didn't feel comfortable with this, but I didn't report anything both for fear of both my reputation being impacted, and for fear of my scores being cancelled on a test that I studied significantly for and potentially did well on. If I were to report any of these incidents, most people would immediately know that it was me who had filed the report, and I would be severely socially ostracised. I did/do not desire this at all. In hindsight, I should have kept it to myself, not expressed my worries to my friends / acquaintances, but unfortunately this did not happen.
In a situation like this, what is the appropriate course of action post-disclosure? Report the student in question and risk negative reputation, a cancellation of scores, and hard work put in (but do the right thing and have fairness reign), or keep the cheating to oneself (and preserve reputation but carry a dishonest weight)?