Naruhodo High school's newest episode
110421 has been aired,
part 1
part 2
part 3
simply search AKB48 なるほど!ハイスクール 110421 I'm sure you can find it through google or youtube
there is still only 3 parts in total, I'm assuming that the file is still uploading,
for what I know it's a 2 hour special,
Everyone please enjoy
for other parts, visit the uploader's channel