The actress showed up two hours early for her hearing, walking hand in hand with her brother, Moore Huffman Jr., who was at her side during her arraignment last month.
There was no sign of her husband, William H. Macy, who's not charged in the scandal.
Huffman is accused of paying $15,000 to rig her daughter's SAT scores. She pleaded guilty to charges of honest services mail fraud and conspiracy to commit mail fraud.
She faces up to 20 years in prison, but prosecutors have said they will recommend between four and 10 months due to her cooperation, in addition to a $20,000 fine and one year of supervised release.
Thirteen other parents have also said they will plead guilty, while others, like Lori Loughlin, are still fighting the charges.