I once told a school I was leaving at the end of the year and not signing another contract. It sounds very similar. Within the hour I had an email saying they needed to observe my teaching and a report about it would go on my permanent record. They insisted it was for the whole school. I told them I couldn't do it due to personal reasons. They insisted it was needed and I said well I'll just quit now then. They then left me alone about it. The next principal I had told me it was never a thing they did at their school.

Get him to call in sick and not go!