By law your juvenile record is confidential and is not a public record. However, I have seen juvenile records information pop-up in private background checks. How private companies get these records is unknown. My guess is that the Clerks of Court have sold them to these companies.
To answer your question, it depends - each agency has its own hiring policies. You should check with the agency that you want to work for to be sure. Do not be afraid to ask - regardless of whether you seal or expunge your juvenile case that information will have to be disclosed to all agencies you apply to. If they want you they may tell you to get the information expunged.
I have represented several law enforcement candidates in your situation so don't give up.
Eric J Dirga
Mr. Dirga is correct about juvenile records popping up in unexpected places. I also think that police departments and certain other agencies can see juvie records upon application of the person for some position or right. Even sealing such a record won't entirely make it disappear from view of these agencies.
If the charges were dropped or dismissed, you can and should move to have the record expunged.
it has been my experience that certain professions such as law enforcement, medicine, the military or teaching may ask about any transgressions while checking your background. Once you are in the respective field you will have union lawyers at your side to help you answer questions within 30 minutes say, if you are a policeman and are involved in a on the job shooting. I consider sealings or expungments somewhat overrated in today's information age. Once your name has hit the public record of a community's arresting agency it may be sold to different marketing companies. You can seal or expunge but in my experience the footprint of arrest will follow you regardless simply because of technology. In a world without computers, having the record sealed at the local courthouse worked.