The Regents exam that high school students are most likely to fail will not be scored under a new system designed to curb score inflation.

In recent years, exams across the city received a disproportionate number of 65s, suggesting that teachers might be bumping up the scores of students on the verge of passing, sometimes illicitly. Aiming to reduce incentives to pad scores, the Department of Education last year began rolling out a system in which teachers are not permitted to grade exams taken by students in their school.

A year ago, 27 schools participated in “distributed scoring,” and 163 schools used the model in June. Overall, the proportion of exams scoring exactly 65, the score needed to pass, fell by half.

This month, all exams for all schools were supposed to be scored under the model. But when the department put out a call for teachers to grade the global history exam, only about 1,000 signed up, officials said. That meant the department was short at least 700 teachers to ensure that all global history exams could be graded on time.

The shortfall means the department’s shift to distributed scoring will be incomplete when students take exams later this month.

“Your school will score its own Global History & Geography Regents exams (as in prior years),” the department told principals in their weekly newsletter.

The global history test posed a particular challenge because it must be given on the last day of the exam period, a Friday, and includes many short-answer and essay questions, which take extra time to score. Schools need to know students’ scores by Monday morning to finish their second-semester schedules or, in some cases, certify students for graduation. Global history, with the lowest pass rate of all subjects, is often the last exam students must pass to graduate.

The department emailed every teacher who is eligible to score global history exams and enlisted the teachers union in recruiting them to sign up to spend their weekend at centralized grading sites.

“After all of that, there weren’t enough applicants to be confident that we could get the scoring done over the weekend,” said Adina Lopatin, the department’s deputy chief academic officer. She said the department has told the state to consider leaving quicker-to-score tests, such as in math, for the end of the week when it puts together next year’s test schedule.

For now, the department is encouraging principals to set up scoring so teachers at least do not grade their own students’ exams, an arrangement that is possible in schools with multiple teachers licensed in the same subject. In small schools, where there might be just one or two history teachers, that probably won’t be an option.

Lopatin said she anticipated that to the extent that global history tests received a disproportionate number of just-passing grades in the past, they would again this year.

“The Global scoring will be similar to what it has been in the past, so I don’t think we’ll see a reduction of that problem this year,” she said. “But I don’t think we’ll see an increase.”