A good opening scene will engage the reader. It should make the reader want more. Action is one way to achieve that goal but, by itself, rarely enough. For example, if someone gets hit by a bus on page one it's sad and maybe even shocking but if we don't know anything about the victim we remain distant and with minimal concern. If the person is a beautiful young woman pushing a baby carriage, we may be nudged a little more toward learning more about the tragedy. If thousands of hundred dollar bills flutters out of the carriage and away in the breeze as the woman bleeds to death on the pavement, now we've got a real reason to turn the page. Why did this woman have so much money in a baby carriage?
Anyway, the point is, make the reader care about your story or your characters in the opening lines. Give them a reason to engage and commit. A "hook" is really a reason to care. Your job is to invent one and introduce it as quickly as possible.
This is as true for young adult as it is for adult novels.