I have noticed that as a new instructor, the hardest thing for me to do is keep everyone interested. I think part of this is the age range of the students, but as a new instructor I know that there are ways I can improve. Any suggestions?

I just started being an instructor, and have very high standards in general. I have found the curriculum and course outlines where I am on a regular basis don't meet my standards, and the students are not challenged one day, and the next two they can't keep up it is so difficult. Any pointers on how to fix this, while not undermining my superiors?