The city teachers union issued subpoenas yesterday to former Schools Chancellor Joel Klein and notices to 11 other education officials as part of a legal battle it launched last year to save 19 schools from closure.

The case concerns schools that were initially given the ax in 2010, then granted a reprieve.

When many of those schools returned to the chopping block the following year, the United Federation of Teachers filed a lawsuit claiming the city had reneged on a written agreement to give support to the schools before taking any steps to shutter them.