ordained minister; regular teacher
A formal title for a fully qualified minister or teacher, especially in Christian contexts. The 'regular teacher' sense is less common and may appear in older educational settings.
He was appointed as an ordained minister of the church.
That school requires a regular teacher's license.
教師 is the general term for teacher; 正教師 specifies a fully licensed or ordained teacher, as opposed to an assistant or trainee.
Compound of 正 (せい, 'regular, proper') and 教師 (きょうし, 'teacher, minister'). The exact historical derivation is uncertain, but it follows a common pattern for formal titles.