The Opposition accuses Ontario's Liberal government of cheating by including students who take five years to complete high school in its graduation rate.
Ontario has had a four-year high school curriculum since 2003, but the government still incorporates students who take a so-called victory lap in its graduation rate.
The government says the grad rate for last year was 82 per cent, but admits only 73 per cent of students completed high school in four years.
Progressive Conservative education critic Lisa MacLeod says even the auditor general criticized the government for the way it measures the graduation rate.
She says the Liberals have been caught cheating and haven't had the success they claim, despite throwing hundreds of millions of dollars at the problem.
NDP Leader Andrea Horwath says the Liberals seem happy to fudge the numbers, and by any calculation missed their target of an 85 per cent grad rate by 2010-11.
Auditor general Jim McCarter took the Liberals to task in his annual report for not publishing a four-year graduation rate for high school.
He said reporting the four-year rate would show how many students can finish the curriculum in the allotted time and how often schools deliver the curriculum as scheduled.