At some point, even the tone of school changed similarly. In elementary school there weren't really grades. I think we got check marks or something like that, then in 6th grade/middle school there were "grades" and maybe even rankings of students. There were also myriad competitions in almost every activity, like in band there were rankings of players "1st chair", and so on, plus spelling bees, competitions in presentations, etc... Of course there were organized sports as well, so kids began training to be on the football team or whatever.
All the organized judging and rule based games are supposed to be training for "the real world", which is theoretically a bunch of similar competitions. I heard warnings from adults maybe 1,000 times that I'd be a loser if I didn't work hard, or that if I didn't buckle down and study I'd be a bum. As I noted in the previous post, "the loser" character is really the invisible fence of the boomer world, or the corporate/consumer society.
I guess the purpose, or maybe just a side effect of all the competitions in school is students internalize a phony model of reality, that is, there is a merit based hierarchy all throughout life that's determined by work and talent and judging. Maybe you suck at sports, but you can win the spelling bee, or maybe go to the chemistry olympics, or vice versa, you suck at chemistry class, but are a starter on the football team and so on. That is, there's always some "fair", real competition you can participate in.
One fairly useful observation is that almost every game is arbitrary and even the competitions are fraudulent or severely distorted in the sense that the rankings are really meaningless. For example, in high school football in the US, there are divisions of schools because some high schools only have 150 students and others have 3,000 so a kid who might be the quarterback on a Division IV football team might not even get on the varsity Division I football team. That's true in almost every type of organized sporting event I ever participated in as an adult. The competition is divvied up so people are participating against "peers" rather than the whole population of athletes, like in running races there are age groups, or in cycling races there are skill categories.
In professional sports, which is ostensibly the closest thing to the "real world" form of competition, that is an unlimited contest which reveals who is really the best, there are myriad arbitrary rules. In fact, in many pro sports the rules accumulate endlessly. In pro cycling, for example, there are all kinds of rules about how much your bicycle can weigh, what the geometry is, the position you can ride in, and on and on. Most pro or olympic level sports have all sorts of rules about the substances an athlete can take to eliminate the use of 'roids and HGH and such.
Another aspect of this competition internalization is people seek counterfeit representations of merit via "status" symbols like expensive cars and houses or sporting goods. In almost every case, a person gets their "status" object like a house with a giant pile of debt. Then they retain their status symbol by avoiding loser status, usually by grinding away at a shitty corporate job for their whole life.
Anyway, quite ironically, it turns out that the elementary school view of games versus the high school competitions forever corresponds to the "real world". That is, there's no gamified reality except the shared hallucination of the general public who's been trained to participate in it.