The subordinating conjunction occupies a fuzzy area. Calling such words conjunctions might be confusing at times. Perhaps, it would be better to avoid the naming issue here except to move back to the word's role in a sentence constituent. This discussion also exemplifies the value of discussing parts of speech last and with reduced emphasis. In that discussion the student can learn about the structure of English sentences.
Interjections are like the color white.
White is created by mixing all colors together. I'm not going to give you a homework assignment. I think you have a final exam to prepare for.