The School System
I actually discuss this a bit in the CardCaptors' section, but it applies to all anime. In straight dubbing or subtitling the shows are not edited for culture. That means that grades (as in "are you in 11th grade or 10th") and days are not adjusted to make them Western. That can confuse a lot of people. And it shows in fansites when people say, for example, that Tory Avalon is in 10th grade because he is in year 2 of high school. That isn't true.
In Japan the school system follows the Junior High pattern, rather than the Middle School pattern. This means that elementary (or primary) school consist of grades kindergarten through 6th. Middle school (or Junior High) consists of grade 7th through 9th, and High school (or secondary) consists of grades 10th through 12th. That means that if a series says someone is in the second year of High school they are actually in 11th grade. So now we don't have to wonder why all these 17 year olds are in 10th grade - they aren't! They're in 11th just as they should be. That's why they have a bunch of 15 year olds running around Middle school too (like Kagome in Inuyasha). Weren't most people you know 15 in the second half of their 9th grade year?
Fans should also note that high school is optional in Japan. High school must be tested into and always costs to attend. Generally high schools are very strict about grades and working outside jobs. Because the schools are private they all have their own rules. Some require uniforms, others do not. Many require their students to join clubs and some forbid students to take jobs. They may also have rules of conduct which must be observed off school grounds as well as on. Those who choose not to go to high school may enter a trade school or go out to find full time jobs. in other words, high school is very much like college is in other countries. Also, though Japanese consider their children minors into their twenties (I'm not sure exactly when they are considered adults, but I believe it is at some point in the early twenties), because they can quite school and get full time jobs at sixteen they often have much greater freedom and even live on their own at this age, whether they go to school or not.
The other note I would like to make on the Japanese school system is that they go to school six days a week instead of five. That's right, Monday through Saturday, for everyone. So, if they aren't at school, it's either a Sunday or they are on Holiday. Unless the series has been Westernized. They also go to school from early morning (generally 7am) to the evening or late afternoon (5pm in most series I have read).
Also, the Japanese see Spring as the rebirth of all things, for this reason their school term starts in the spring. It runs (generally) on a trimester system, with a longish break in summer and in winter. They always have homework on these breaks and generally have a school trip (optional or not depending n the school, the travel distance, and the costliness) somewhere over the break.