District officials say about ten students at Trabuco Hills High School are under investigation.
They're accused of cheating on an advanced placement exam last month, by text messaging on their cell phones.
"I think they come in with their phones in their pockets and there's a teacher that's just looking at them, but not watching every single individual every second they're taking the test," said student Steven Graffio.
Authorities say the students facing the accusations will not be allowed to attend prom Saturday.
And if found guilty of cheating, they won't be able to take part in extra-curricular activities for one semester.