Covenant Theological Seminary in St. Louis, Missouri, has made several classes available for free online through their Worldwide Classroom.
Although Ancient and Medieval Church History is a college-level course, I believe it would be appropriate for a high school student studying this topic.
In order to listen to these free classes, you’ll need to register with Worldwide Classroom. After registering, you’ll be able to listen to all of these sessions on Mp3, as well as download written transcripts and study guides for each lecture.
Here is a course description and a list of the topics covered in this course.
Course Description (taken from the Worldwide Classroom site):
A study of Christianity from the Early Church to the dawn of the Reformation, with source material readings. This course places an emphasis on the application of church history to life and ministry and helps the student to understand the development of Christian thought and the formulation of doctrine as part of God’s overall pattern of history. This course is taught by David Calhoun.
Lesson 1: The Study of Church History
Lesson 2: The Growth of the Christian Church
Lesson 3: The Persecutions
Lesson 4: The Apologists
Lesson 5: Orthodoxy and Heresy
Lesson 6: Canon, Creed, and Bishops
Lesson 7: The Early Church Fathers
Lesson 8: The People of the Early Church
Lesson 9: The Church in the Fourth Century
Lesson 10: The Beginnings of Monasticism
Lesson 11: Donatism
Lesson 12: The Council of Nicea
Lesson 13: Cappadocians and Constantinople
Lesson 14: Ambrose, Jerome, and Chrysostom
Lesson 15: Augustine’s Confessions
Lesson 16: Augustine and the Pelagian Controversy
Lesson 17: Augustine’s Theology of History
Lesson 18: The Council of Chalcedon
Lesson 19: The Early Middle Ages
Lesson 20: Medieval Missions
Lesson 21: The Christianization of Great Britain
Lesson 22: Learning and Theology
Lesson 23: Eastern Orthodoxy
Lesson 24: The Late Middle Ages
Lesson 25: Medieval Monasticism
Lesson 26: Crusades or Missions?
Lesson 27: The Waldensians
Lesson 28: Scholastic Theology
Lesson 29: Thomas Aquinas
Lesson 30: The Sacramental System
Lesson 31: Church and State
Lesson 32: Wycliffe and Hus
Lesson 33: Reform in Italy
Lesson 34: Mysticism and the Modern Devotion
Lesson 35: The Waning of the Middle Ages
Appendix A: Catholic World Missions
Appendix B: The Spread of the Western Church
Appendix C: The Spread of the Eastern Church
Appendix D: The 100 Most Important Dates in Church History