The first half was enjoyable, but the second half was really disappointing. The first 14 episodes are a charming story about a boarding school in England. The rest feel more like a modem Japanese high school, the characters personalities change, and the stories become trite. I've now read the books that this is based on and know that the last 12 episodes are original and not from the books at all.
When I started watching this, I wondered why it wasn't more popular, but now I know. I struggled to finish the series and only my strong completionist tendencies saw me through.
If this series sounds interesting to you, I would suggest not going to the trouble of tracking down a copy of the DVD and read the books instead. They're quick reads and, since they were written in the 1940's, they're in the public domain. Unless you're in the US were copyright is a century long :(