In June, Desiree Smith was graduated from Murry Bergtraum High. Her grades were in the 90s, she said, and she had passed the four state Regents exams. Since enrolling last month at LaGuardia Community College in Queens, Ms. Smith, 19, has come to realize that graduating from a New York City public high school is not the same as learning.

She failed all three placement tests for LaGuardia and is now taking remediation in reading, writing and math. So are Nikita Thomas, of Bedford Stuyvesant Prep; Sade Washington, of the Young Women’s Leadership School in East Harlem; Stacey Sumulong, of Queens Vocational and Technical; Lucrecia Woolford of John Adams High; and Juan Rodriguez of Grover Cleveland High. “Passing the Regents don’t mean nothing,” Ms. Thomas said. “The main focus in high school is to get you to graduate; it makes the school look good. They get you in and get you out.”

Mayor Michael R. Bloomberg has made the rising graduation rate — to 61 percent in June, from 46.5 percent in 2005 — the No. 1 symbol of his educational accomplishments. But that rate is less impressive when paired with the percentage of graduates who need remediation in all three subjects when they enter LaGuardia or other City University of New York community colleges: 22.6 percent in 2010 (2,812 students), up from 15.4 percent in 2005 (1,085).

“A few years ago, we noticed the numbers really jump,” said John Mogulescu, the senior university dean for CUNY. Over all, 74 percent of city high school graduates enrolled at the system’s six community colleges take remediation in at least one subject, but those needing all three are at the highest risk of dropping out. So in 2008, CUNY started a program with a few dozen students to see if an intensive semester focused on just the three subjects — five hours a day, five days a week — could make a difference. The program, known as Start, has since expanded.