Hey there @FREAKINGREXIS! If your installation is from the launcher, then you can’t control which minor version you’re on, it will always update to the latest since the minor version changes are hotfixes and shouldn’t break compatibility with older projects.
However, if your school uses 5.4.2 specifically and you must have a 5.4.2 install specifically, you’ll need to build the engine from it’s source code to avoid upgrading projects from there. If that’s the case, head on over to this link and follow the instructions to get invited to the Unreal Engine github team and be allowed to see and download the source code.
https://www.unrealengine.com/en-US/ue-on-github
https://github.com/EpicGames/UnrealEngine/releases/tag/5.4.2-release