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, ofBedford Stuyvesant Prep; Sade Washington, of the Young Women’s Leadership School in East Harlem; S...