Yes! No problem!
Let's us quickly sum it up for you: We're going to ask you about it on the form, you have to mark that the main characters are two teachers, or three, and from there we get down to work and we'll do everything in the plural. In this case you'll have to have a photograph (just ONE!) showing the two of them, or the three of them, together. It can also be a framed collage.
If you'd prefer that the teacher is the main character, but you want the teacher assistant or any other teacher to also appear in the story with their photo, then include them as if they were just another child.
Of course we adapt the gender of our stories, whether the teacher is a boy or a girl, of course!