This song is so good there are seven full versions of the song, a TV version with all 31 girls, an acoustic version, and it got played in the alternate retelling of the Series Negima!?  The basic premise of the anime is a 10-year old boy magician becomes the English teacher of a middle school all-girls academy.  This boy, Negi Springfield, is in charge of 31 girls all older than he is.  As far as the anime goes, I personally found myself liking the first series than the Shaft retelling.  The second series can be great at times, but it's so much different from the canon in the manga.  The first series follows the manga more closely, but the deviates in the final 4+ episodes.  The way to go through this series is through the manga.  It felt awesome for about 300 chapters and is lumbering towards the finish line in the past 50+ chapters towards what many perceive (including myself) as a rushed ending.  (I'll address the flaws possibly next week when the series concludes.)  But as for the anime, the OP theme called "Happy Material" is one of the more catchier OP themes I've heard in recent years.  I stated that there are seven versions of it which features only a part of the class and each version is basically a remix of the original.  I'm bias and leaned towards the More Rock version because Shizuka Ito is in it.  For the sake of this post, I'm posting all seven since I don't hate any of them and are all brilliant in their own right.

Happy Material Lyrics