OVERBROOK HIGH School has not had a biology-certified teacher since September.

The 129 students enrolled in biology, instead, have seen their teachers reassigned, classes changed and little instruction in the biology lab since the fall for a course that is a state requirement for high school graduation.

And the biology-certified teacher set to begin today at Overbrook, according to a school district official who spoke earlier this week to Philadelphia magazine, has rejected an offer to teach at the school, the district confirmed yesterday.

"The candidate declined for personal reasons," said district spokeswoman Raven Hill. The district will continue to seek a biology-certified teacher for Overbrook, she said, adding "this issue highlights the difficulty of recruiting candidates midyear for traditionally hard-to-fill positions."

While the search continues, the class that the 10th-grade students initially enrolled in as biology had its title changed in the fall to "environmental science," Overbrook staffers say.

The reason behind the change was so the "children wouldn't be forced to take a test they didn't have the education for," said an Overbrook source, speaking anonymously for fear of retribution.

When report cards were issued yesterday, students in the course were given grades, but the class name was "mysteriously whited out," said teacher Bonnee Breese, the Philadelphia Federation of Teachers building representative and an executive board member of the teachers union.

"Oh, God, it's almost as if they don't want anyone to know what the class is," said the staff source.

The school district did not respond to further questions from the Daily News.

At the start of the year, there were seven biology classes and in November that number was cut down to five, Breese said. One class was assigned a substitute, and the other four were taught by a math teacher with a background in science. Nearly 25 percent of the science students are special-education students.

Then last month, five teachers were asked by Overbrook principal Angela Thompson to cover the classes, which were moved to the computer lab. Now students are learning through an online program, receiving information and taking tests until they reach a target score during each class, Breese said.

"I keep laughing to keep from crying. Seriously, I really do," Breese said.

The district stands behind the online biology program. It's aligned with the district's curriculum and the state's Common Core Standards, Hill said.

Another Overbrook staffer, who also spoke on condition of anonymity, says the online setup doesn't work for kids.

"We need a teacher. I don't think the students can learn from technology alone," the staffer said. "Children need to have information presented by an actual person and that's a teacher."

On Twitter: @ReginaMedina

Online: ph.ly/DNEducation