I miss the idea of school "houses", as captured in Harry Potter (Gryffindor, Hufflepuff, Ravenclaw, Slytherin) and Kid Nation (Red, Blue, Yellow, Green).
I attended Hagen International Primary School (HIPS) in Papua New Guinea, from 1980 - 1985. So from Prep to Year 5. All contract workers sent their kids to the International School. After Year 6, kids would then go to nearby Bamboo Heights, which was the international high school. So I went to school with kids who were from different parts of the world: United Kingdom, Australia, New Zealand, Philippines, Africa, India, United States, Canada, China, Burma, etc. and of course there were also native Papua New Guinean kids. Basically our parents were hired by the Papua New Guinean government as teachers, bankers, engineers, construction workers, etc. to help build up the main towns like Port Moresby (which is the capital), Mt. Hagen, Goroka, Lae, etc.
So in HIPS, we had three "houses" named after native birds of Papua New Guinea: the Eagle (Blue), the Hornbill (Red), and the Cassowary (Green). I was a Cassowary. My friends were scattered Eagles, Hornbills, and Cassowaries. So Houses didn't "pick" friends. But when we had to divide into our Houses for inter-school and intra-school events, friendships are on pause *hehehe*. How we were assigned to the colors were actually quite random, when you enrolled as a new student, you were just placed in the color that was next in line after the last enrollee. I don't recall being given a choice, otherwise I would have asked to be an "Eagle". That's because during my time there, the Eagles were the most balanced in scholastics & athletics :)
Every week during Assembly, the House Captains would go around each classroom together and tally up the points. Then in Assembly, the Head Master would update the bar graph and we would see which House was ahead. Points were earned in different ways. You did something commendable in the classroom, the teacher would award points. You had the cleanest section during School Clean-Up Day, then your House would get points. You win points for your House during Sports competitions. Etc. Bad behavior could also earn negative points.
So there was plenty of motivation to excel in school activities. And plenty of motivation NOT to screw up. Houses can encourage, but also open up opportunities for bullying. I unfortunately went through a phase of being a hotheaded bully who could bring scrawnier scaredy-cat kids to tears. How sad. Thank goodness it was short-lived :)