Post secondary education is a s7 expense.
The current method being used is that the parents pay 2/3's the costs of post secondary expense proportional to income, AFTER bursaries, scholarships and other grants are deducted from the total. The child is expected to contribute to their own education, thus the 1/3 remaining.
So, assuming equal incomes of the parents, it works out something like this (numbers completely assumed):
Cost of College + residence = $10,000 per year
Bursary/Grant received by the child = $2,000
$10k-$2k= $8k
$8k/3 = $2,666.67 payable by each parent for the kids education