It was Rushdoony (1994) who wrote:

It is a serious mistake to see theology as an academic exercise.  The word theology means God’s word; it begins with the presupposition that Scripture is the word of God, and the duty of the theologian is to understand it and to apply it to every area of life and thought. … For me theology means the total mandate of God through His word.  What I have written only scratches the surface; it is an introduction to the subject, and it is written to move men to faith and action.  The neglect of theology in our time is in part due to the theologians, who have multiplied the various divisions, so that, among the divisions of study have been Biblical Theology, Systematic Theology, Dogmatical Theology, Exegetical Theology, Practical Theology, and so on.  The areas of study also include such subjects as Natural Theology and Speculative Theology.  With the inventions of so many variations, it is no wonder that both pastors and people have lost interest in the subject and avoid it (Rushdoony, 1994, p. xv).

There are many useful theological texts, beginning with Rushdoony’s two volume set, that would be helpful on the shelves of a home-based educating family:

Berkhof, L. (1941). Systematic Theology. Edinburgh, Scotland: The Banner of Truth Trust.

Conner, K. J. (2004). The Foundations of Christian Doctrine. Melbourne, Victoria: KJC Publications

Grudem, W. (2009 ). Systematic Theology: An Introduction to Biblical Doctrine. Grand Rapids, Michigan: Zondervan

McNeill, J. T. [ed.]. (1960). Calvin: Institutes of the Christian Religion in Two Volumes, The Library of Christian Classics, Volume XXI. Philadelphia: The Westminster Press.

Reymond, R. L. (1998). A New Systematic Theology of The Christian Faith, Second Edition. Nashville, TN: Thomas Nelson Publishers

Rushdoony, R. J. (1994). Systematic Theology In Two Volumes. Vallecito, California: Ross House Books

Rushdoony points out the importance of theology when he writes:

The churches of our time seem to believe that God exists to save man and keep him happy. … But the world is not governed by your and my will and wishes, but by the triune God and His eternal decree.  Until we learn that fact, and say Amen to it as persons and societies, we shall only gain God’s wrath and judgment.  Of course, our humanistic age finds the wrath of God a remote concept; it will soon learn other wise, because God is God (Rushdoony, 1998, p. xvi).

Let us carefully deliver the Faith to future generations, as once delivered to us, through the line upon line, precept upon precept study of sound Biblical theology.

References

Rushdoony, R. J. (1994). Systematic Theology In Two Volumes. Vallecito, California: Ross House Books