Students getting remedial instruction at LaGuardia Community College.Credit...Robert Stolarik for The New York Times 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 Y