Did you create the catalog on the flash drive or, if not, did you copy it onto the flash drive?
If so, you first have to open the catalog in LR, using the File/Open Catalog function. Browse to the .lrcat catalog file you created, and open it.
From there, it will just be a question of whether the new catalog has the references in place for the images on the flash drive. If you had the catalog on the flash drive at your school, then the catalog should "remember" them. Otherwise, the catalog will show thumbnails and previews, but there will be a question mark, indicating that the catalog doesn't "see" the image files.
If you do see the question mark, then go to a "parent folder" in the Library Folders panel that has the question mark, and right-click and choose to "Find" the missing files/folders, browse to the proper place in your flash drive and select it.
Lightroom is "smart", in that once you locate an upper-level "chunk" of your missing folders/files it initiates a "smart search" of adjacent folders and files.