What is the ruling on money received by a teacher who does not perform her work and relies on others to cover for her?

If a woman signs an employment contract for teaching in exchange for a salary, she is not permitted to take the salary unless she performs the required work, as fulfilling contracts is obligatory. If the official overlooks her attendance without authorization from the higher authority, then he is complicit in sin. However, if she works in a private institution and obtains permission not to attend from someone authorized to do so, then the salary is permissible.