The 16-year-old was assaulted in dark toilets at Fenelon-Notre Dame, a private Roman Catholic school in the Atlantic port city.
Investigators hope to find a match for DNA traces found on her clothing.
No such mass testing has been done before at a French school, AFP news agency says. The test is voluntary.
Saliva samples will be taken from 475 students, 31 teachers and 21 other adult males who were on the premises at the time.
While the testing, by plain-clothes police, is voluntary, any male refusing to take part could come under suspicion.
Two classrooms are being used for the collection of DNA, which is due to end on Wednesday. The school has nearly 1,300 pupils in total.
All the DNA samples testing negative will be destroyed, AFP reported, quoting local prosecutor Isabelle Pagenelle.
据BBC网站4月14日报道，去年九月，一名女孩在法国拉罗谢尔一所学校被强奸，因此法国警方对学校500多名男学生和工作人员进行了DNA样本检测。
这名16岁的女孩在菲尼圣母中学黑暗的厕所被袭击，这所私立罗马天主教学校位于法国临大西洋西部的一座海港城市。
调查者希望能够找到与女孩衣服上相符的DNA。
法新社称，之前在法国学校从未有过这么大规模的检测。检测是自愿的。
警方将会对当时在校的475名学生，31位老师和另外21位成年男子进行唾液样本检测。
尽管检测由便衣警察负责且是自愿的，但是任何一位拒绝参与的男子都可能受嫌疑。
两间教室用于DNA采集，将于本周三结束。这所学校总共有大约1300名学生。
法新社引述当地当地检察官Isabelle Pagenelle的话说，所有呈阴性的检测结果都会被毁掉。
