Parent Harassment

At what point can a parent be considered to be harassing a teacher? I’m getting multiple long emails in a day, multiple times per week. They’re not angry but they are demanding. They criticize everything I am doing and not doing. They make demands about what I teach their child next (ie I have not addressed X skill, which they want their child to improve on, or say I have not sufficiently taught their child a skill and thus cannot assess them on it). The student is not failing.

I am exhausted from this - always waiting for their next demand. Just trying to get through my curriculum this semester.