Delay in approval

You can file a writ petition, though pensioner cases take some time

Agree with RS

Let the teacher first make a representation in writing venting out the grievances to the competent authority through proper channel.

If there is no response or no fruitful result  is available even after reasonable waiting period, the teacher can escalate the matter through legal channel, by first issuing a legal notice to the authorities concerned.

After that the teacher can either approach the civil court for recovery of its dues or approach high court directly with a writ petition seeking direction to the school authorities to settle the dues expeditiously with interest accrued, if any.