Is the additional money earned from working in elementary grades permissible, with a request to work in grades not included in the bonus to cover the deficit, and to fulfill the same number of periods?

If the supervisor is authorized by the school owner or the employer, then there is no harm in disbursing the reward for teaching the sixth grade. However, if he is not authorized, then it is not permissible to disburse it to the supervisor or the applicant, due to the absence of the condition for its disbursement. This is based on Allah’s saying: "O you who have believed, fulfill [all] contracts," and the Prophet’s (peace be upon him) saying: "Muslims are bound by their conditions."