The following items introduce students to the Holy Spirit, as part of the mystery of the Holy Trinity:

Holy Spirit Lesson – Student Handout       

God as Trinity – Artwork Lesson

Holy Spirit Lesson – Student Task

Meaning and importance of the Holy Spirit

Why is it important for Christians to believe in the Holy Spirit

Going deeper…

And from CatholicIreland.Net; John Paul Sheridan provides an

excellent overview of what the Scriptures and Church teaching

tells us about the Holy Spirit in this article: The Holy Spirit