Honestly, it seems to me that sometimes being Slytherin af does get you 'ahead' in life. No, it's not always the people with integrity that 'succeed' - often cheating, manipulation, corruption and undermining others is quite effective.
But that doesn't mean that it's worth it.
Scores feel like the be-all and end-all, but they're just... really not. (Okay, there are some areas where they do matter deeply, e.g. getting into med, but I'd argue that people don't have just one calling in life that's the only way they'll ever be fulfilled and valuable.) Your relationships, your character, your integrity, your mindset, your maturity: they honestly matter so much more in the real-life job market. At work, you're typically expected to work together as a team (I'm now wondering what percentage of job ads use the words "team player" or some equally meaningless equivalent).
Your co-students are displaying insecurity, immaturity, selfishness, pettiness, and a rockin' scarcity mindset that's going to damage them for a long time. These are the games that immature children play. Yes, lots of people play them well into adulthood. Lots of people treat team-based work as a single-player exercise where their role is to undermine others to show their own individual brilliance - I definitely feel the urge often enough. And it sometimes works. It really, really sucks.
But at what cost?
Your relationships and mindset and integrity are what are going to matter to you in the long run, and I can't see how it's worth it to set up a habit of undermining these - of undermining happiness for yourself and others - just for a score.
(Oh, and yeah - I really do think that explaining concepts to others is one of the absolutely best ways to learn.)