The IDI has two parts. You can begin with part 1 if you have younger students (up to fifth grade). If your students are older you can begin with part 2. The beauty is that if your older student does not master the beginning skills assessed in part 2, then you already know what you can do. You can assess using part 1. The missing skills are revealed and you have a framework for helping each reader fill the holes in their reading skills.
If you use the IDI and find it helpful. Let me know if you did find it helpful, or even if you didn't! I'd really love to hear how you use the information that you gain from this inventory, and how your students are progressing!
Happy Reading!