In addition to the gun tallies, 1,767 students reported bringing another kind of weapon - a knife or club, for example - during the same time frame.

That's 4 percent and 8 percent respectively of the survey respondents, rates slightly below national trends, according to district officials.

About 21,000 students (out of 28,000 enrolled) participated in the middle and high school safety surveys, and their answers seemed to validate previous results from surveys that relied on much smaller sample sizes and statistical extrapolation.

But the raw numbers brought home the daily reality of guns and other alarming conditions in the city's middle and high schools.

"I don't think any principal here can deny ... that everyday there's got to be a gun on campus and we just don't know," said Guillermo Morales, principal of Thurgood Marshall Academic High School. "I would be very naive to say we don't have that problem here."

Morales said one gun has been confiscated at his school this year.

School officials said that while some of the numbers are indeed alarming, school safety is not an isolated issue. Students often bring weapons or guns in their backpacks or pockets because they feel unsafe on their way to and from school, Morales said.

"It's not because the kid has an incident here at school, it's because they have to get on a bus and get back to Hunters Point at night," Morales said. "I have kids who will stay here until 7, 8, 9 at night in the hope that someone, a teacher or someone, will give them a ride home so they don't have to get on the bus and go home."

While the survey results were available in the fall, district officials kept them off the public's radar until Wednesday, when they posted summary reports in the Student Support Services section of the district's Web site.

"This was already data we had," said Trish Bascom, associate superintendent of Student Support Services, adding that the district took time to check accuracy. Bascom said the district has many programs that decrease weapons in schools and raise awareness of safety.

The survey, conducted by ETR Associates of Scotts Valley in the 2007-08 school year, gives San Francisco school officials a depth of information they've never had before - statistics and raw numbers for each school site.

That information wasn't released with the summary reports.

District officials said they haven't provided that data because the response rate wasn't high enough at some of the schools to accurately reflect the students' opinions at those sites.

Based on prior state and national survey samples, San Francisco is not alone in grappling with safety concerns; districts across the state and country face similar issues at comparable rates.

"It's disturbing, but it's important information for us to have," said school board member Jill Wynns. "It gives much more information about the reality of kids' lives."

The new comprehensive survey asked students dozens of questions, including many from a biannual statewide school safety questionnaire.

According to the survey:

-- 455 middle school students (6 percent) and 923 high school students (7 percent) said they were gang members.

-- More than half of the 21,000 respondents said they don't feel teachers and staff keep them safe from bullying, verbal harassment or physical violence in the classroom.

-- 630 middle school students (8 percent) and 1,132 high school students (9 percent) said they didn't go to school at least once in the previous 30 days because they didn't feel safe.

-- 60 percent of students felt safe or very safe at school.

District discipline policies require automatic suspension and a referral for expulsion for any student who brings a firearm or replica to school. Carrying a knife is grounds for suspension and possible expulsion, officials said.

Elementary school students in the fifth grade were included in the latest survey, but the response rate and required parental permission numbers were too low to accurately reflect the opinions of fifth-graders across the district, officials said.

E-mail Jill Tucker at jtucker@sfchronicle.com.

This article appeared on page A - 1 of the San Francisco Chronicle