Is it permissible for an online school that teaches Islam to charge a student a fee if they are absent from a lesson, or if the session is canceled due to their failure to attend within 30 minutes, while reserving the right to change the lesson's timing?

There is no harm in obligating the student to pay the lesson fee if he is absent by his own choice. If the lessee has utilized the benefits or the period has elapsed without any impediment to utilization, then the wage becomes due. If changing the lesson time deviates from a prior agreement in the contract, the school may change it and demand the fee if the student is absent, for the Prophet, peace and blessings be upon him, said: "Muslims are bound by their conditions."