Continental typically rounds up less than 500 miles. Don't belive garbage people on planes tell you. Second it could be their company gets some "comped" platinums. This happens with high rev corporations. And the whole one flight concept is not a good benchmark. One flight to HKG is about the difference between silver and gold, or gold and platinum.
The real issue is the last minute problem. If you registered for the last SAT of the year and had to miss it. Will the colleges admit you without it? Good execuse or not... sometimes life happens. It's not the companies job to modify the rules. CO tries to be fair. But you'd be shocked at the number of people who want to be rounded up to due some reason. How to you start judging the reasons? What is a valid reason? And more importantly, IS it fair to those that fly the required miles? Let's not be hypocrites. We get VERY upset on this board about comped Elites taking our upgrades.
My advice is take that missed trip now. It will put you well on the way to a higher status level.