Preaching is a slippery term.  Everyone knows what it is, but it is notoriously difficult to define, especially when attempting to contrast it with the closely related concept of teaching. ... And though they are certainly not the same, I'd like to offer five ways in which they are similar, and by which it can readily be seen that Christian education is radically different from the education offered by worldlings.

...

3)  The Christian educator, like a preacher, has a view towards real life change.  The preacher knows that biblical truth is not simply to be known or felt, nor is it enough even that it lead us to worship, if these responses do not elicit real change in the lives of the hearers.  But in the Christian worldview, all truth, deposited in every body of knowledge across all disciplines, has been given by God in part for this end.  So the Christian educator leads his students to ask questions like "What does God expect me to do with this information?"  "How does what I have just learned change the way I will live, work, and make decisions?"  "How will God be glorified and known in my life by what I am studying?"  He trains their minds to ask these questions, and presses them for real life changes.  If students leave the classroom unchanged, then Christian education has not occurred.

4)  The Christian educator, like a preacher, announces, heralds and proclaims good news about what God is doing in the world.  Every Christian is called to herald the good news of the Father's salvific activity to reconcile His people to Himself in Jesus Christ.  This Good News has implications for every area of life and enormous eschatological significance for every corner of God's creation.  God is active, not passive, in His creation.  The Christian educator, as he teaches in his field, announces to his students what his discipline proclaims concerning what and how God is working, for God has everywhere left Himself a witness to these very things.  However, facts do not speak for themselves.  They must be interpreted through a Christian worldview and the implications heralded in the classroom. 

5)  The Christian educator, like a preacher, must be aware that he may be speaking to both the willing and the unwilling, the interested and the indifferent, or even the friendly and the hostile. Even in a classroom of professed believers, there may be resistance, both passive and active, to embracing higher education in the way that is consistent with Christian theology.  The Christian educator may very well have to woo and persuade his students with words convincing and full of grace.  Therefore he must be interesting, passionate, winsome, and he must pray about his task.  He cannot enter the classroom as if he is just laying information at the students' feet and it is of no import if they pick it up. It is of great import.  It may be the difference between a life well lived in service to Christ and a life wasted.

A Christian educator is therefore very much a preacher of whatever discipline with which he has to do.  He does not merely teach the fields of mathematics, or language arts, or biology, or economics; he preaches them.  He is a preacher of higher learning, and his sanctuary is the classroom, for it is here that God is brought near to the minds of students made eager to know Him by the operations of the Spirit.  The image called forth by the use of this word preach is really much closer to what a truly Christian educational process looks and feels like than what the word teach commonly connotes today.  The Christian educator who takes his business seriously will take up the challenge, no matter his field, of "gripping the hearts" of the students entrusted to his care for the sake of the One who bought them.