Hello,
The language packs only translate the Graphical User Interface (GUI), i.e.: buttons, menus, labels, help messages and so on. You (and your pupils) are the solely responsible for the course content.
So, the language packs goal is not to translate content for you.
However, there is a built-in mechanism in Moodle (the multilanguage filter) that allows for content to be shown in various languages, depending on the user's settings. But I'm speaking about a static, pre-translated content.
Regards,
Orestes.