A common policy seems to be to allow for limited stacking where outside scholarships can first replace expected student loan or work or unmet need, but then reduce grants from the college before reducing the expected parent contribution.
But each college may have a different policy, so each college must be checked individually.
Oh…one other possibility in addition to what I posted above.
Some schools allow stacking up to the cost of attendance. BUT there are others that expect you to pay your family contribution so that does not get reduced.
BUT ask…because policies vary.
They will tell you…you need to speak to a financial aid officer. The person answering the phone usually is NOT a financial aid officer. So…ask to be transferred to one.