Family and neighbourhood are

Concept: Socialization is the lifelong process through which individuals learn the norms, values, and behaviours of their society. Sociologists of education broadly distinguish the agencies that carry out this process by how informal/personal the group is and how early in a child's life it typically becomes influential. Groups that are informal, intimate, and among the earliest a child engages with are commonly grouped in one tier; larger, more formal institutions that typically become influential somewhat later in childhood are grouped in the other tier.

Application: The family is the first social group a child is born into: it transmits language, basic values, emotional bonds, and cultural practices before the child has meaningful contact with any structured institution. The neighbourhood extends this same informal, face-to-face influence into the child's early surroundings, reinforcing what is first learned at home. Both are informal, intimate, and among the earliest influences in a child's life -- so both are commonly classified in the earliest, most informal tier of socializing agencies.

Cross-check: Contrast this with school, a formal, structured institution the child typically joins only once these earlier, informal influences have already begun shaping early behaviour -- confirming that family and neighbourhood, being informal and early rather than formal and later-arriving, belong in the opposite, earliest tier.