misteacher
/ˈmɪstɛtʃər/Definitions
1. noun
A person who is not a certified teacher but claims to be one, often for financial gain.
“The school board was suspicious of the misteacher who had been hired to teach mathematics.”
2. noun
A person who is unqualified to teach but assumes a position of authority.
“The new principal was accused of being a misteacher who was more interested in politics than education.”