An 18-year-old man pleaded not guilty Wednesday to being an accessory to a shooting that injured three people in front of a San Francisco high school Monday afternoon, a district attorney’s office spokeswoman said today.Jacquez Tucker was seen driving a car away from the scene of a shooting at 18th and DeHaro streets, about a block away from International Studies Academy High School. The shooting happened around 1:30 p.m., 10 minutes after summer classes let out, police said.Students ran back to their classrooms, some screaming, while officials locked down the campus, police Sgt. Lyn Tomioka said.One female student was grazed in the leg by a bullet. All three victims are expected to survive, Tomioka said.Two guns have been retrieved, including the one police believe was used in the shooting.Police said Wednesday the suspected shooter is a male who was being charged with attempted murder. However, Tomioka said today Tucker is not believed to be the shooter, and that the shooter is still at large.Tucker also pleaded not guilty to evading officers and gang enhancements. He is scheduled to have a date set for his preliminary hearing on June 25.