Taiyo to Umi no Kyoshitsu [太陽と海の教室] Better than GTO in my opinion [Rating: 10/10] This drama has much better "lessons" than GTO. Some of them are very very wise and deep. Granted it might not be as crazy as GTO but still it has its moving and entertaining moments. First 3-4 episodes are a bit slow but afterwards the pace picks up quickly.
WATCH IT! You won't regret it a single bit.