CHAPEL HILL - About a dozen students -- not four -- have been accused of cheating on a mid-term exam or entering Chapel Hill High School at night to obtain teachers' answers to tests, Principal Jackie Ellis said.

In an interview Thursday, Ellis corrected misinformation given Tuesday at a school district press conference, where spokeswoman Stephanie Knott said an isolated incident involved four students. Knott said the students were caught on school security cameras using a master key to break into the school to obtain answers to a social studies mid-term exam.

Actually, Ellis said, students who cheated did not use a master key to the school to obtain the answers. A student used a camera phone during school hours to photograph a teacher's answer sheet for a few friends taking the exam later, Ellis said.

This month, a student told the teacher about the cheating. Administrators questioned those involved. Two students confessed, and others admitted receiving the answers but said they didn't use them. Those students had to retake the test.

The master key was discovered when students questioned about cheating told administrators that other students had the key and were using it to obtain test answers.

So far, school officials can't prove students with the master key cheated because they don't have surveillance video showing who entered the school and when. Old footage was lost during an upgrade to the cameras in January, Ellis said.

All in all, 10 to 12 students have been implicated in either the cheating or master key incidents, Ellis said. About five of them are accused of using the master key, she said.

"We continue the investigation," she said.

Faculty and other seniors have felt angry and betrayed, Ellis said. Seniors worry that their class will be remembered for these revelations instead of their hard work.

"It is an outstanding senior class," she said.

Some faculty members have told Ellis the students should face harsher punishments.

The two who confessed to cheating received zeros on the exam and likely an F for the semester, Ellis said. They were also suspended, along with the two students who confessed to unlawfully entering the school with the master key.

Students involved also face the possibility of removal from any honors societies into which they have been inducted. In addition, the final report for most colleges and universities, along with a final transcript, requires the high school to send a statement describing incidents such as suspensions.

"That is clearly not a slap on the wrist," Ellis said.

Ellis said she is considering pursuing criminal charges for unlawful entry, but is leaning against it.

She also has not ruled out contacting high school graduates about the master key. Right now the investigation is focusing on current students.

Ellis, who is new to the school this year, sees the incidents as a teaching opportunity.

She had already noted a 2007 yearbook story called "Cheating: How Students Got By" that included a pie chart suggesting 80 percent of students admitted cheating. Faculty also identified cheating as an area they wanted to address this year.

The school improvement team had already set up an academic integrity committee, which has been meeting weekly since January, Ellis said. That committee recently surveyed homerooms to assess the cheating problem. Ellis is working on getting information about cheating and academic integrity posted in every classroom.

"We will make this school a school of honor and integrity," she said.