Gunfire Near School Badly Wounds Boy : Violence: The teen-ager had just registered for classes and was leaving campus with his mother and brother. Police suspect gang activity.

A 15-year-old boy was shot in the back and seriously wounded Monday morning as he, his brother and mother left the parking lot of a Sun Valley high school where the two boys had registered for class.

Manuel Yepiz of Sun Valley was hospitalized at Northridge Hospital Medical Center, the boy’s mother, Remedios Yepiz, said. Police said he was in critical but stable condition after he was struck at least once by bullets fired from a passing white van. No arrests had been made Monday, police said.

Police believe the shooting at John H. Francis Polytechnical High School is gang-related, although the victim’s mother denied that her son is a gang member.

The shooting occurred the day before school was to open and amid increased uniformed Los Angeles police patrols near the campus, where students include members of several rival East San Fernando Valley gangs. Patrols are increased each year at the start of school, Lt. John McCrillis said.

“Because of the school year, we are bolstering our presence around the school,” McCrillis said. “It gives us a better measure of control when there is a visible uniform presence.”

School Principal Virginia Holt said the number of school district police on duty at the campus would be increased during the first week of school because of the shooting. In the past, one guard was posted on campus.

About 300 students were waiting in line to register or were milling about the grounds of the 2,360-student school when the shooting occurred, Holt said. She said a drive-by shooting occurred near the school two years ago, but that no one was injured.

The victim was registering as an 11th-grader when he and his brother walked out of the parking lot and through the school’s Arleta Avenue gate about 10:50 a.m., said the boys’ mother while her son was being treated at the hospital.

Remedios Yepiz, who was walking behind her two sons, said several shots rang out from a passing white van. At least one bullet struck her son in the left side of his back.

The brother and another male student dragged the victim into the schoolyard. Paramedics transported the boy to the hospital.

Los Angeles Police Detective Mark Aragon said police suspect that the victim was a member of a gang based in Sun Valley and that the van passengers belonged to a gang centered in Pacoima.

“You have a lot of rival gangs going to school here,” Aragon said.

Aragon said the victim had no arrest record, but that he had told police in the past that he belonged to a gang. The brother also claimed gang membership, Aragon said.

Remedios Yepiz said her son, who was smart enough to skip 10th grade, was not a gang member.

“He’s never given me a problem,” she said. “He’s so smart.”

She said she did not see the occupants of the van long enough to identify them. “This came so quick, I didn’t see anything,” she said.

She said the shooting has convinced her to remove her sons from the school and enroll them in a private school.

“No more,” said Yepiz, who has lived with her husband and four children in Sun Valley for 12 years. “Forget it.”

Paul Sims, a music teacher who heard the shots and was among the first people on the scene, doubted that increased guards could prevent another drive-by incident. “You can only be so many places at once,” he said.

Some students said they were shaken by the incident. John Pagani, 15, who was registering as a 10th-grader, said, “It’s pretty dangerous, I guess.”

But several others said they assumed that the incident was gang-related and they did not fear for their safety. “This only happens to gang members,” said Araceli Contrares, 15, who was registering as an 11th-grader Monday. “Not to us.”

“I’m not really worried,” said Joey Gozun, 16. “I don’t have any enemies. If you keep to yourself, you’re OK.” Then he added, “Unless they use you as a target.”

Times staff writer Michael Connelly contributed to this story.