Notice: This will only work if your school has the Respondus locking extension. Your school will also need to have IXL SecureTest.
So basically, you go to this page: ixl.com/securetest
Once you have Respondus, you want to press the button that says "Launch IXL SecureTest." Once it starts closing your tabs and disabling your extensions, do the shortcut Ctrl + Shift + W. (An easier way to see when to do it is by bookmarking some extensions on the bookmarks bar, then doing the shortcut when those extensions start disappearing.)
Once you open Chrome again, or whatever browser your school uses, everything should be unblocked (except for Wi‑Fi filters).