Prosecutors have charged a total of 50 people, including the college consultant at the center of the scandal, William Singer, who has already pleaded guilty to racketeering and other charges. Thirty-three parents are accused of paying Mr. Singer to arrange for cheating on entrance exams or conspiring with him to bribe coaches or athletic officials to get their children admitted to colleges as recruits to sports teams, on the basis of fake credentials.

On Monday, prosecutors said that 13 of the parents, including the actress Felicity Huffman, would plead guilty. In all but one case, those parents will plead guilty to a single count of conspiracy to commit mail fraud and honest service mail fraud. Then on Tuesday came indictments, including new counts, against many of the parents who had not announced plans to enter guilty pleas.

Vassili Thomadakis, a former assistant United States attorney in the district of Massachusetts, said Mr. Singer would almost certainly be sent to prison for some period of time, even though he has cooperated with the investigation, including making recorded phone calls to parents at investigators’ request. Mr. Thomadakis said it was also likely that any coaches or administrators who were convicted would face prison time, perhaps for a matter of months or a few years.

Less clear, it seemed, was what might happen to any parents convicted in the case.

Former prosecutors said that might depend on an array of matters. How much did the parents spend on the scheme to get their child into college? Did they opt to plead guilty? Did they fight the charges through a trial, but get convicted anyway? Did they cooperate with the authorities?

“For folks who have these kind of the bigger payments that you see in the indictment, I think that they certainly face some prison time, especially if they take the case to trial and lose,” Mr. Thomadakis said. Mr. Thomadakis said that prosecutors are likely to argue that a sentence of some prison time is necessary to dissuade other parents eager to do anything to help their children get into college from engaging in similar behavior.