The state's curriculum watchdog investigated 65 alleged breaches of exam rules in 2015, up from 38 the previous year.

In one case, a student peeked at photos of a draft essay on their mobile phone to cheat their way to a higher grade during an exam.

Another student hid notes in a dictionary, while four students copied their classmates' answers during the high stakes exams.

Almost 30 per cent of all cheating matters involved a mobile phone.

The Victorian Curriculum and Assessment Authority penalised 10 students for "serious breaches". Some students had their grades reduced by up to four grades, and one student had their results cancelled for a subject.

VCAA chair Chris Wardlow said most students understood that cheating was a waste of time.

"It's unfair to yourself and your classmates. Students who do appear before review committees are deeply remorseful for their actions," he said.

Mr Wardlow said the authority would continue to work with schools to ensure students stopped bringing mobile phones into exams.

"There is no excuse for students to bring mobile phones into the exam room," he said.

The figures only include cheating during VCE exams. Students also cheat during their VCE course work. Caulfield Grammar is currently investigating allegations that a student had hacked into a teacher's computer to gain access to VCE assessment tasks.

Serious cases of cheating are referred to the VCAA's review committee, which conducts hearings with an experienced lawyer to determine penalties. The penalties always exceed any potential advantages.

The punishments range from reducing the students' marks to receiving a warning where there was "no intention to cheat". The authority reprimanded 18 students and cautioned 29 students for minor breaches in 2015.

Last year the authority banned smart watches from exams because the devices "have the capacity to store, receive and transmit information".