If you search for "GarageBand unblocked" on Google, you will likely find third-party websites offering "free downloads" or "modded versions." Do not download these. They are often vectors for malware, adware, or viruses.
To make music in a restricted environment like a school, you should use browser-based Digital Audio Workstations (DAWs) that function similarly to GarageBand. Recommended Unblocked Alternatives garageband unblocked
ChromeOS devices (Chromebooks) do not have the native architecture or operating system files required to interpret Apple software packages. The Best Unblocked Online Alternatives If you search for "GarageBand unblocked" on Google,