The OW will have created an image of you in her head. It may well involve you being deficient in some way. Not having enough sex with him, not devoting enough time to him, not being a good enough housewife or cook, not caring for him when he is ill, or any other number of similar scenarios.
Sometimes this image is formed based on how the OW interprets what the MM says about his wife. E.g. 'she's out again tonight', the OW will interpret the wife as being a selfish party girl who leaves him alone in the evening.
Sometimes the OW won't need any encouragement to form a negative image of the wife; her sub-conscious guilt reflex will create an imaginary harridan.
The OW will be thinking these types of things until the MM breaks up with her then, depending upon the circumstances of the break-up, she will either continue to believe in the image she has created, or, she might start to revise her image of you. You might actually become human in her eyes, she might start to confront her guilt, she might start to feel ashamed at what she has done, or sorry for you.
If OW knew you would be teaching her own daughter I would suggest this raises her level of selfishness to a whole new level. I am not saying any teacher would let this influence his or her professionalism, but if I was a OW parent I would not want to risk anything that could affect my child's education. That would include steering clear of shagging the husband of any member of staff at the school of my child.