California Law defines the make-up and purpose of the school site council.

CALIFORNIA EDUCATION CODE

Section 52012 A school site council shall be established at each school that participates in the school improvement program authorized by this chapter.  The council shall be composed of the principal and representatives:  teachers selected by teachers at the school; other school personnel selected by other school personnel at the school; parents of pupils attending the school selected by such parents; and, in secondary schools, pupils selected by pupils attending the school.  At the elementary level the council shall be constituted to ensure parity between (a) the principal, classroom teachers and other school personnel; and (b) parents or other community members selected by parents.  In schools with fewer than three teachers, this requirement may be met by establishing a council that is composed of equal numbers of school staff and parents or other community members selected by parents.  At the secondary level the council shall be constituted to ensure parity between (a) the principal, classroom teachers and other school personnel and (b) equal numbers of parents or other community members selected by parents, and pupils.  

The basic principle behind the SSC is that those individuals who are most affected by the operation of their school should have a major role in the decisions regarding how their school functions. It is the role of the SSC to advise the principal and staff on the planning, implementation, and evaluation of the school improvement plan, and to allocate categorical funds from the state and federal levels to support the goals of the school plan.  The SSC reviews the progress of the school in achieving the goals of the plan.