Wow, what did she eat(as well as some of the other students) to get boobs that big!? Remember, they're supposed to be middle school students, so I'm wondering if it had to do something with what they ate. If it is, they should have it mass-produced and sent all schools or directly to homes right away!
After some revisions to my initial google searches, it appears this is part of an OVA set called "Mahou Sensei Negima! Mou Hitotsu no Sekai" and the second episode of it.
Neither did I ! Neat ! Also, great shot of Chisame, who's probably my favorite of Negi's followers. A tsundere girl with glasses who's a closet cosplayer / otaku ! She's likely among the most clear-thinking and observant of the girls... Unfortunately, she also seems among the most unlucky, too.