- "Teachers are hereby banned from giving students any information that is not strictly related to the subjects they are paid to teach"
- —The Decree[src]
Educational Decree Number Twenty-Six was the third Educational Decree created by Dolores Umbridge in her capacity of Hogwarts High Inquisitor.  This Decree forbade the teaching body from giving the students any information that was not related with the subjects they were hired to teach.
Educational Decree Number Twenty-Six was passed by Dolores Umbridge, then-Hogwarts High Inquisitor on 14 January, 1996 to prevent the teachers from discussing the mass breakout from Azkaban that had occurred the day before. 
After the Decree was passed, small groups of two or three professors would be found around the school talking ín a low and urgent voice, discontinuing their conversations every time a student approached. As the teachers were apprehensive about this Decree, the students made it the object of many jokes; Lee Jordan quoted the Decree to Umbridge when she told off Fred and George Weasley for playing Exploding Snap in her Defence Against the Dark Arts class. As a result, he was forced to write lines with her Blood Quill. 
The decree was abolished after Dolores Umbridge's suspension from her post of High Inquisitor and Albus Dumbledore's return to his post of Headmaster, following the Battle of the Department of Mysteries in the spring of 1996.