Trying to remove macOS Monterey

Hey guys! I am trying to remove a partition of macOS Monterey on a 2009 MacBook Pro. I installed Monterey using open core and I was wondering how to remove it because I wanted to use el Capetian. Just to note, MacOS Monterey IS CURRENTLY installed alongside el Capetian. I used recovery mode but the Monterey partition isn’t here even though I could boot into it.