There are many, many people that play basketball, including elementary school kids, middle school kids, high school kids, college basketball players, NBA players, WNBA players, female players in schools, other countries, etc.
There are around 1000 NCAA basketball schools in total, with 351 schools in 32 Division I basketball conferences. There are also other divisions, but only Division I gets shown on TV, and contains most of the players that go into the NBA.
There are 295 Division II Schools.
That is the division below division I. Division one is where the top schools play while division two is for schools who don't attract many athletes or are a small school.
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1,000 schools participate at the NCAA division 2
There is no roster limit but only 36 players may be on scholarship. Division I allows for 85 players on scholarship and Division I-A allows for 63.
Division 1 schools can have varying numbers depending on the sport. Currently, basketball has the most with 344 teams in Division I.
25,000
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There is no education required for basketball players. Other than basketball knowledge, there is no education required. Thus, many players do not have college degrees (in the NBA or WNBA).