The wraparound jacket of the 19th volume of Akira Hiramoto's Prison School manga, which will go on sale on December 4, has announced an OVA of the series.
The OVA will be released with the 20th volume of the manga, which will go on sale on March 4, 2016. The staff and main cast of the TV anime will return for the new episode, adding Mikako Takahashi (Hachimitsu to Clover) as the voice of Mitsuko Yokoyama.
Prison School's TV anime adaptation aired in 12 episodes earlier this year between July and September. A live-action TV drama adaptation was also announced in August and has been airing since October.
So, this OAD will adapt the Mad Wax Arc (chapter 82~87), basically continuing were the first season left off.
It's also nice to hear that Yokoyama Mitsuko will be voiced by Takahashi Mikako, I haven't heared her voice in a while.