Opposition to Mr. Sessions among their ranks, judges said, is more about the pressures he has put upon the office than about his stance on immigration.

Immigration courts stand apart from the judicial system. Cases are often complicated by an absence of documentation and supporting evidence, defendants’ failure to understand American laws and lack of a lawyer. Proceedings can be time-consuming. Many families and individuals have their cases denied, making courts emotionally charged places where crying and screaming are familiar sounds. Judges often burn out, Mr. Schmidt said.

The immigration judges report to a Sessions appointee, James McHenry, the chairman of the office that oversees them. His office controls which cases they will hear and can force judges to prioritize certain cases and send them around the country to work. Mr. Sessions has assigned 18 immigration judges to work at detention centers near the border, about a 50 percent increase in the ranks of judges handling immigration cases in those areas.

In a speech on Monday at the judges’ conference outside Washington, hosted by the Justice Department, Mr. Sessions asked them to look for inefficiencies to finish cases more quickly.

“We have to be very productive,” he said. “Volume is critical.”

Three judges said they were struck by his emphasis on speed, prosecutions and policy matters without acknowledgment of the need to balance those demands with ensuring due process for immigrants. They said they feared the focus on metrics and closing cases would make it harder to sort through complicated cases and easier to simply deny applications for entry into the United States.

Scores of attendees wore American flag pins in support of “judicial independence and integrity in our courts,” according to a note accompanying the pins.

Dozens of judges who gathered early Monday evening expressed anxiety over their treatment, according to one person present who was not authorized to share the details of the private meeting.