Notice to employee who resigned without fulfilling his notice period

Hello,
I work at a school and a teacher has resigned abruptly without giving us a chance of looking for his replacement. He did not fulfill his notice period as agreed when he signed his offer letter. We would like to send him a letter informing of the same. Can anyone please share a template of a letter so that we can inform the ex-employee of his responsibility towards the school as per the contract he signed. I would also be grateful if anyone with more experience can share what other document templates a small school HR Department would require. Thank you.

Date -
To,
Mr. ________
___________
Subject - Discontinuation of services without serving notice period.
Sir / Madam
This refers to your resignation letter dtd ____________ whereby you have resigned from the services of our organisation. You are aware that as per clause number ___ of your Appointment Letter dtd _______, you must give a notice of __ month towards your separation from the services. However, with disregard to the said clause, you have abruptly stopped reporting on duty from the next date of your resignation.
Your such act has caused great difficulties to us since we could not even found suitable replacement of your position. Due to this reason, the work and functioning of our organisation has suffered badly.
You are advised to report on duty immediately, upon receipt of this letter, failing which we shall be forced to take appropriate action against you.
Regards
Signature....
Adv. Manish Gadre
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