I disagree with those who say you need to disclose. Why? Because you were not legally an adult and were not in legal control of your actions. If they try and deny you passage for that, they'll run into all sorts of problems.
There is a reason that your juvenile record is sealed. Unless you were tried as an adult for a crime, I don't think there is any duty to disclose for an action you had no control over, and no reasonable person would judge you as an adult for.
Also, if there was a duty to disclose, where would it stop? High School? Middle School? Elementary school? I don't think anyone can argue that punching a child in the face and having a temper tantrum in 2nd grade will need to be disclosed on C&F for a graduate school. The only reason that something should be disclosed on C&F is to determine if that person posseses moral fitness to become a lawyer (
Because that bar is clearly so high). This will not affect it. Therefore, it should not be disclosed.
(once again, not a lawyer, this is not legal advice, blah blah blah. Merely common sense.)