A/N According to Buffydotfandomdotcom, Buffy's High School graduation class appears to have had 95 students that graduated or least participated in the actual graduation. The battle included some older students that fought with Angel, but that 95 total doesn't include them. Buffy's class announces they have the lowest mortality rate in the history of the school, this after thirty - fifty classmates, depending on which website is doing the counting, says died and doesn't include the number of teachers that died over the two and a half years Buffy attends High School there.
It's never mentioned how old the High School is and it's one of three named High Schools, the other two being Kent Preparatory and Fondren High School. Their class sizes and mortality rates are unknown, but at least one student from Kent was meant to be fed to Machida and the three used to make the female Frankenstein Cordelia was almost part of came from Fondren.
Class sizes at the beginning of Sunnydale would have been much smaller, with much smaller mortality numbers. But rate and numbers are different things. 30 plus 95 is a starting number of 125. 50 plus 95 is 145. So when Xander, Jesse, Willow and Cordelia start their freshman year they may have been part of a total number of students that's between 125 and 145, in that year. No mention is made of new classmates from families moving into Sunnydale during this time, except Buffy, so no replacement of dead classmates by new arrivals. Which means anywhere from 37.5 percent to 62 percent of Buffy's classmates died, in the two and half years she attended Sunnydale High School. If that's the lowest mortality rate in Sunnydale High School history, as stated by Johnathan Levinson, what the Hell were the rates prior to that?!
The students noticed, even if they rarely spoke about it and only the adults 'in the know' seem to notice. In a town of less than 40,000, a number that began dropping after the Mayor died by more than 10,000 before the mass exodus when the First was haunting Sunnydale in season 7. 😨
Even if say thirty students a year died (that's being conservative) over the course of a century, from each grade, that's 3,000 teenagers in each grade. Each. Over the course of a century. Four High School grades means 12,000 teenagers and that's just one school in Sunnydale. If the numbers were the same at the other two High Schools than that's 36,000 teenagers, nearly the same as the combined total of the population of Sunnydale at the time of their graduation.
Over the course of a century. The town I graduated High School from had about 25,000 people when I graduated. They once ran an article that the murder rate in town had doubled from the year before. From 1 murder to 2 murders.
I may be wrong in my numbers as I took Honors English, Literature and History and barely scrapped by with a C in any Math class I was in. 😵
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"I've pulled random obituary columns from the Sunnydale Times going back a century." Rupert Giles brought up the next point. "A disportionatly large number of teenagers appear in each column and that cause of death varies, but most often appears to be 'wild animal attack causing neck rupture'. Sunnydale doesn't even have an official dog catcher and never has, the Zoo has only been up and running for approximately a decade and no animal has ever been reported as escaping from it. The dead lion was reported as it died of an illness."
"The lion Xander and Faith ate when they were possessed." Diana muttered.
"Indeed." Rupert took a bracing sip of tea before continuing. "Unusual events most often appear to be gas leaks, animal attacks and gangs on PCP. Biker gangs were often blamed in the fifties and sixties and hippies got a very bad rap in Sunnydale in the sixties and into the seventies as handing out drugs to naive teenagers."
"Crime statistics like that would catch attention." Aaron commented. "So why haven't they?"
"They're not being reported as crimes." Rupert answered. "But as runaways for the most part, many seem to get caught up in gangs or drugs or at least are suspected of being caught up, but since the gangs are a Los Angeles problem, they're not actually being reported as such by the officials in Sunnydale. Just as cause of death and occasional articles in the newspaper."
"But how long has the Hellmouth actually been active?" Diana asked.
"I believe to a certain extent it may have been active since Sunnydale started nearly a century ago and has begun to dramatically increase it's energy output beginning a couple of years ago." Rupert answered. "And I believe it's possible it's been somewhat active going back centuries. The Chumash, a local First Nations Tribe and the Spanish Colonists all recorded stories that are eerily similar with high numbers of people dying, most attributed to illnesses that may not have actually been illnesses. The numbers seem consistently high."
"Sunnydale's a death trap." Diana said grimly. "But we still haven't figured out who set the trap."
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A/N Giles tells Buffy in the first episode that the history of Sunnydale includes many odd occurrences that may include zombies, werewolves, incubi, succubi (although those last two aren't referenced in any other episode.)