In education, we like to mention "fair use" whenever we want to use a source and for some of the resources they fall within the realm of fair use when we are using them for educational purposes. For example, when you want to use a small portion of Martin Luther King's "I Have a Dream" speech as it is published in your textbook you are definitely within copyright and fair use guidelines to do that. However, if you create some amazing learning activities around King's "I Have a Dream" speech for your students and package them with the sound recording of the speech that came with your textbook for sell on Teachers Pay Teachers you have just exceeded the bounds of fair use. See if you were just creating those lessons and sharing them with your students you are fine. However, the moment you take the resources you have created for your students (which is within the scope of your work) and sell them to others with copyrighted material in them so that you can make money you have crossed the line.
According to the Copyright Basics, a work created as an employee does not belong to the employee but to the employer. So, to publish that