Konnichiwa.
I'm Japanese, and I did learn about WWII in history class at school. I looked back my history textbook I used at school, and it is written in it. And for people who is interested in WWII, there are various kinds of books about it in bookstore and there are programs about it on TV sometimes, and also many informations on internet. No ones hiding about the war at school or in our society.
About young people, there are many kinds of young people in Japan. Some are interested in history, but some aren't. The ones who are interested in it, or who likes studying, would take the class eagerly, and maybe study by themselves reading books other than the textbook, and knows about it quite well. The ones who take class normally, would know the outline about it. But there are people who's not interested in history at all, or who doesn't like studying. Those people may be not listening or even sleeping during the history class. Then they would not know about WWII very much. And also there are many kinds of teachers. Good ones will teach details about history and make students get interested, but not good ones just reading the textbook, would make students feel boring. I think it's just the same as other countries.
Maybe you would meet some Japanese who doesn't know about WWII well, but it's not because we're not taught about it at school, or the goverment or whatever is hiding about it. It's because of the person's interest, or ability. But most people who's older than 23 (I don't know about the younger people because I don't have chance to talk with them), at least know about Pearl Horbor attack (not all knows the year of it), and when and how the war ended. If someone says he/she doesn't know about it, he/she would be seen as person who is lacking common sense in Japan too. And if young ones says they don't know about it, we would be depressed also.
(Sorry for my poor English. I hope it makes sense.)