The phrase "interim principal" means a temporary or short-term person who takes on the role and responsibilities of being the principal in a school until a permanent principal is found. Full definition
There have also been many questions regarding placement of the acting interim principal. (queensbp.org)
LaFayette Superintendent Jeremy Belfield said he wants to hire a former Homer school district administrator as interim principal at the Onondaga Nation School. (nystateofpolitics.com)
At the end of the school year she took on the role as Interim Principal while the principal was out on maternity leave. (eagleprep.org)