Go to the meeting and apologise for your actions. Don't approach it in any other way as you are likely to get booted out - simple as.
As was said, don't try and shift the blame by saying "so and so does it also and I thought it was ok / fun /a test for you etc etc... "
You have to understand that this is an educational establishment where people are trying to do their jobs. Every year they have a very small percentage of problem kids / adults - who think they are funnier/smarter than everyone else - who decide to play pranks/jokes or say things that they have heard/seen a million times before.
Most importantly your actions prevented them from doing their job and they don't really owe you anything. They aren't liable for you and with the attitude you are displaying to them, they can let you go and not have to justify removing you from the course as you are currently a liability to them wasting resource time/money and educational hours on stuff that shouldn't have to be done.
Take a step back from what you see as your side of things, and appreciate how they see it. You need to mature-up quickly, because if you think this is tough - a job is 10 times tougher. And without the education - actually getting a job will be not just tough - but highly unlikely.