"I didn't see the teacher yesterday."
Translation:Yo no vi al maestro ayer.
Is " Yo no vi el maestro ayer" also correct?
Because, when the direct object is a specific person, we always add a before, and since the direct object is el maestro, it becomes a + el maestro = al maestro
Because lo is the direct object pronoun. The teacher is the direct object here (hence why personal a is being used) I see him - lo veo. I give the book to him - le doy el libro (because here he is the indirect object = le = to him here)
Are you sure you written "Yo no vi a la maestra ayer" and not "Yo no vi la maestra ayer"?