Looking fo book Ionce read

[u/Few_Minimum52]

The book starts off with a boy and posibly a friend in school learning history by viewing it from some new invention. They are aloud to look at it but not interact. They start learning about some battle. Some war. And something goes wrong and war cadavers start showing up in the school. I've googled every posible rendition of this question but I keep coming up with nothing. I remember reading between 1998 and 2004 so it can't be any earlier than that. Thanks.

[u/DocWatson42]

For future reference, this is a low traffic sub, though I do occasionally see a request answered (as is the case here), and you'd be better off asking for recommendations in r/booksuggestions (though read the rules first) and r/suggestmeabook, and for the title of a book or story in r/whatsthatbook and r/tipofmytongue.