When the Department of Education releases a new set of letter grades for high schools today, some schools could see their scores change substantially.

That’s because the latest progress reports, which the city uses in part to decide which schools to close, are the first to incorporate data about how well schools have prepared graduates for college. The shifting metrics reflect the department’s growing recognition that a high school diploma does not guarantee college success.

The new data look at the percentage of students who passed college-level exams or courses; met City University of New York proficiency standards; or entered college, the military, or a work training program, and together they make up 10 percent of each school’s score. Most of the information appeared on last year’s progress reports but did not factor into schools’ grades.

For the most part, the new data points do not work in schools’ favor. For the last two years, the city has boasted a four-year graduation rate over 60 percent. But city and state assessments of students’ college-readiness during the same period found that only about a quarter of students were ready for college four years after entering high school. The wide discrepancy means that the new metrics could easily depress some schools’ overall scores, particularly because the department reduced the weight on graduation rates and credit accumulation to free up the points.

Indeed, Deputy Chancellor Shael Polakow-Suransky said last year that he expected many schools to see their grades fall once the college-readiness metrics counted.

The High School of Violin and Dance in the Bronx, for example, received an A from the city last year after posting a 76.5 percent 4-year graduation rate — but every single member of the Class of 2011 would have been required to take remedial courses at city colleges, according to the department. The school is located on the Morris High School Campus, which Mayor Bloomberg cited as a success during his State of the City speech in January.

Yet features of the progress reports and changes to the college readiness metrics are likely to mitigate against falling scores. Most significant is the fact that, as with other items measured on the progress reports, schools are rated based on how they compare against other schools’ past performance. Schools whose students are relatively more prepared for college should do well on the college readiness metrics, even if most of their students do not graduate college-ready.

In addition, responding to criticism from principals, the department broadened its definition of post-graduation success. Originally, schools were set to get credit only if their students enrolled in college. Now, they will get credit if students enter the military or enroll in certain job training or public service programs. Plus, schools will get some credit for students who graduate college-ready, even if they don’t finish high school in four years. And the department has revised other rules so that schools with more high-need students who meet the city’s standards earn more extra credit points.

But in general, the city seems prepared to allow schools to net lower scores. While elementary and middle school grades are assigned according to a fixed distribution, so that no more than 10 percent of schools can earn F or D grades, the department sets no limit on the number of high schools that can earn low grades. Last year, about 12 percent of high schools that got letter grades had D’s or F’s.

The openness to lower scores jives with several other policy changes aimed at resetting expectations that are underway at the Department of Education. After an internal audit revealed opportunities for graduation rate inflation, the department moved to tighten controls over how schools award credits and to hasten the switch to a new system of Regents exam grading meant to cut down on inappropriately high scores. Starting this year, new limits on students’ ability to make up missed credits is likely to cut into schools’ credit accumulation statistics.

The high school progress reports were originally set for release late last month, but the department postponed the announcement after Hurricane Sandy hit. Principals have known their schools’ scores for some time. The department will use the scores to help generate a list of high schools that it will consider closing. Last year, the department closed 23 schools, nine of them high schools, during the regular closure process, and some suspect that the closure list could be even longer last year.

Asked about school closure plans in the last year of his administration, Bloomberg said in April, ”Pick a number. It’s less than the total number of schools that are in this city and greater than zero.”