Presbyterian government is by councils (known as courts) of elders. Teaching and ruling elders are ordained and convene in the lowest council known as a session or consistory responsible for the discipline, nurture, and mission of the local congregation. Teaching elders (pastors) have responsibility for teaching, worship, and performing sacraments. Pastors are called by individual congregations. A congregation issues a call for the pastor's service, but this call must be ratified by the local presbytery.