Final answer:
Informal methods for holding youth accountable outside formal justice systems are known as informal negative sanctions, which rely on community norms and personal relationships to enforce behavior standards.
Step-by-step explanation:
Informal methods of holding the youth accountable while avoiding entry into the formal justice system are referred to as informal negative sanctions. These are methods that arise naturally within a community or society and can take various forms. They do not require the establishment of formal mechanisms and rely on the strength of personal relationships and community norms to moderate behavior. When a youth violates these norms, they may face consequences such as disapproval or social exclusion, rather than legal penalties. These sanctions are meant to maintain order and address minor infractions without escalating to the formal legal system.