The school may require the teacher to prepare lesson plans for her leave before she goes out on leave. she cannot be required to perform work from home after she goes out on FMLA leave.
If there is a reason why the teacher cannot complete the lesson plans before her leave begins, she should discuss the issue with the school before her leave begins. It would not be a good idea to leave the school under the impression that the lesson plans are going to be complete, then leave the substitute without some or all of the lesson plans.

