The actress Lori Loughlin and her husband, the fashion designer Mossimo Giannulli, were also charged and were not among those who prosecutors said on Monday would plead guilty. The government has said that the couple conspired with Mr. Singer to pay $500,000 in bribes to get their daughters admitted to the University of Southern California as recruits to the women’s crew team, even though neither actually rowed crew. Ms. Loughlin has lost some professional opportunities as a result of the charges — most notably, the Hallmark Channel said that it would stop development of shows that feature her.

It is not clear what impact Ms. Huffman’s acknowledgment of guilt will have on her career. She has roles in several coming movies and television series, including playing the prosecutor Linda Fairstein in the mini-series “When They See Us” about the so-called Central Park Five, five black and Hispanic teenagers who were wrongfully convicted of beating and raping a female jogger in Central Park in 1989.

Prosecutors said that Ms. Huffman and most of the other parents would plead guilty to a single count of conspiracy to commit mail fraud and honest services mail fraud. The charge carries a maximum sentence of 20 years in prison, but it is unclear how much time, if any, Ms. Huffman and the other parents will receive.

Their sentences may be affected in part by how much money each is alleged to have paid to Mr. Singer and others as part of the scheme. Ms. Huffman’s payment of $15,000 was among the smallest, according to court documents. Ms. Huffman’s and the 12 other parents’ sentences are also likely to be lighter as a result of their pleading guilty and not making the government go to trial.

In addition to the parents, prosecutors said on Monday that one of several coaches charged in the case, Michael Center, the former head coach of men’s tennis at the University of Texas at Austin, would also plead guilty to the same crime. Prosecutors said that Mr. Singer paid Mr. Center $60,000 in cash and directed $40,000 to the University of Texas tennis program in exchange for Mr. Center designating the son of one of Mr. Singer’s clients as a recruit for the tennis team, even though he was not a competitive tennis player and did not ultimately play on the team.

Two parents, Bruce and Davina Isackson of Hillsborough, Calif., have also agreed to cooperate, prosecutors said. The Isacksons were accused of paying Mr. Singer $600,000 to bribe athletics officials in order to secure their two daughters’ admission to U.C.L.A. and U.S.C. as athletic recruits, and to cheat on their younger daughter’s ACT.

According to the criminal complaint against Ms. Huffman, her husband, William H. Macy, was also involved in the $15,000 payment to Mr. Singer. For reasons that are unclear, Mr. Macy was not charged.