At the other end was Lisa Williams, an assistant teacher at a Houston high school known as Niki who prosecutors say took bribes — the indictment cites one in the amount of $5,000 — in exchange for allowing cheating on the college entrance exams. The judge noted that Ms. Williams, who entered her plea in a voice barely above a whisper, had qualified for a court-appointed lawyer.

In a sign of the wide interest the case has generated, television cameras and photographers crowded the sidewalk outside the courthouse an hour before the hearing. Access to the courtroom was limited, with some journalists confined to a spillover room. Inside the courtroom, the defendants, their lawyers and family members, and a few members of the public, filled the benches on the left and in the center, while the benches on the right were packed with reporters.

Most of the defendants appeared in suits, but one charged in connection with test cheating, Igor Dvorskiy, the director of a private school in Los Angeles, was dressed informally, in a gray sweater.

Magistrate Judge M. Page Kelley conducted the hearing with the efficiency of an assembly line. She brought the defendants up three at a time to be arraigned. Mr. Ernst came first, and in addressing him about his rights and the consequences of violating the conditions of his release, Judge Kelley instructed the others to listen carefully so that she did not have to repeat herself.

All of the defendants are out on bail, of varying amounts. Those who also appeared on Monday were Donna Heinel, the former senior associate athletic director at the University of Southern California; Laura Janke and Ali Khosroshahin, former University of Southern California soccer coaches; William Ferguson, the former women’s volleyball coach at Wake Forest University; Jorge Salcedo, the former head coach of men’s soccer at the University of California at Los Angeles; and Jovan Vavic, the former U.S.C. water polo coach.

Others included Steven Masera, the accountant and chief financial officer of Mr. Singer’s company and a related nonprofit through which prosecutors say he funneled the bribes; Mikaela Sanford, an employee of Mr. Singer’s who is accused of taking online classes in place of some students so that they could submit the grades she earned as part of their college applications; and Martin Fox, the president of a private tennis academy in Houston, whom prosecutors say Mr. Singer paid for helping to arrange some of the bribes.