The authorship of the New Testament is a not universally agreed among Biblical scholars. Many would not agree that Matthew, Mark, Luke or John actually wrote the gospels that bear their name. However I'll assume you want a fairly traditional approach if you are teaching youth.
There is one thing that is almost universally agreed among scholars and that is that Luke (or whoever wrote the Gospel of Luke) also wrote Acts. They have incredibly similar styles, and Acts refers to "my previous book", so its considered pretty much a slam dunk.
The other candidates are the three letters that bear the name of John, and also Revelation. They are traditionally ascribed to John the Apostle, who is also traditionally considered the author the the Gospel of John.
Neither Mark or Matthew wrote anything else biblical.
You might like to consider getting hold of a Bible commentary, which will give you all sorts of extra information about what is known about the authors. If you are studying at a college level, you should have several of these available in your library.