Otome Senshi Lovely 5!

From Tsundere Translations: Ogdoas Private Academy... Under the new, young headmistress, freedom, independence and self-fulfillment are the motto of this mission school. However, among the nuns there those who are concerned about order and morals within the school and who oppose the head-mistress's ideas. And without anyone knowing, right now, at this school... a battle between good and evil is about to take place! A continuation to Shion and Nashida-sensei's story called "Teacher's Pet" can be found in Yuri Hime Wildrose volume 2