I’ve been sworn to secrecy over my resignation, why is it such a big deal?

I am an ALT, five years in. Last week I got accepted into a Japanese graduate school so I sent my resignation notice to the appropriate board of education people and was called in for a meeting within an hour.

Graduate program starts in April, so I said I would work until the end of March instead of July and they can get a replacement for me in April. Gave them enough time to do this and a generous more than three month notice. They are mad at me, which is fine I guess, but what surprised me more is I was sworn to absolute secrecy outside of the people I already emailed.

Now I do know it is pretty hush hush about other teachers until the official announcements two weeks before the start of the new school year, and I respect that, but why is it so important I keep this top secret?

This is my first job out of college so please forgive my ignorance. Considering the reaction of people who like me a lot over my leaving 4 months early, clearly I am breaking some social rule. Why am I not allowed to tell anyone and why do people seem so mad over this? Like I would be forced by the government to leave in July anyway, but leaving at the same time as the regular teachers is a huge deal apparently.

by Dojyorafish