In youth volleyball teams are divided by age. For example, a team consisting of kids 12 and under is referred to as a "12s team" or "12's team", and they typically play teams in that same division. This age designation can also be paired with other words like "division", for example, "they're holding a tournament for teams in the 12s (12's) division."
I've seen both "12s" and "12's" in use, although "12's" seems more popular in Oklahoma. Which one is grammatically correct?
This is not a question on how to pluralize numbers, but rather a question about whether we are pluralizing numbers (12s) or if this is the possessive usage of a number (12's), or perhaps even an abbreviation (just like "they are" abbreviates to "they're"). In other words, are people implying "this is a team consisting of a multitude of 12s", "this is a team belonging to group number 12", or "this is a 12-and-under team"?