What is the ruling on taking payment for explaining only part of the material and sufficing with that?

It is not permissible for an employee to leave official work hours before they end or to be late for their start without an excuse, because that is a breach of the agreed-upon condition, and Muslims are bound by their conditions. The teacher is like a private employee; therefore, he must adhere to the full working hours, except with the permission of whoever has the authority to grant permission. The employer has the right to deduct the equivalent of the time he did not work. So, he must repent and adhere to the terms of the contract.