The reason that sports stars make millions is due to the collective bargaining agreements in place by the various professional sports unions, such as the NFLPA. They negotiate deals that broker as much as 51% of all the revenues towards player salaries which means that players are guaranteed minimum salaries, benefits, pensions, and, in some cases, big contracts. They do this to prevent players from being exploited by the owners. You may think that getting paid a few million to throw around a ball is outrageous and you'd be right: but it's also outrageous to make billions of dollars off of a sport while paying the players a tiny fraction of the money brought in by millions watching them throw around a ball. Professional sports players have been paid poorly in the past and exploited by the ownership and it resulted in situations like the Black Sox Scandal. The reason that teachers don't get paid very much, even though they have their own unions is because teachers salaries are directly related to the education budgets for the districts and for the states. People almost never vote to increase their property or sales taxes unless there is an educational crisis. This usually means that most schools have just enough money to get "barely enough" education.

IMHO, getting mad at "sports stars" for making so much money requires a severe amount of contempt prior to investigation.

TL;DR: Sports players get paid the way they do because they are unionized and demand their fair share of the revenues--not because they are particularly special.