Cultural Transformation

Recently our friends at 9Marks Ministries wrote to ask:

Does Scripture call the local church (by which we mean the local church as the local church, not as individual Christians) to the work of cultural transformation? For example, is a failing school system the responsibility of the local church?

Here is the answer I gave:
There is a sense in which the answer to this question must be "no."  The church's primary calling is to preach the gospel and to worship God in the ministry of the Word, the sacraments, and prayer.  While the worship of God and the proclamation of the gospel have a transforming influence on the surrounding culture, this does not happen directly, but indirectly, as the people of God live out the implications of their faith in every aspect of life. 
Yet there are also ways in which the answer to this question must be "yes."