If I'm not mistaken; the half life of LSD is reletively short so it should clear from your body within a few days. I'm sure with the right equipment it would be detectable if it's still in your system but you have a couple things to think about.
How much money do you think your school is willing to pay for extensive testing? If this is a common practice for every student then they are less likely to pay to test every student for every drug. If this is a special treatment they've assigned to you specifically then there's a greater chance they're gonna test you for more drugs.
How often are the test done? Are they scheduled or are they sporadic. If the tests are spaced well enough apart from each other then it would be reletively safe if you used your LSD shortly AFTER the test, that way when your next test comes up you will have had plenty of time to clear your system.
That all being said, every persons body is different and the metabolizing time can vary from body to body. Also without further information of how the lab handles the tests we can not accurately tell you much of anything concrete.
Be safe
