Individual Reading Inventories are tests designed to assess a student's reading level and comprehension. They generally focus on one aspect of reading, such as pronunciation or contextual clues, and are used as parts of many standardized tests.
When assessing a student's reading level, most schools use more than one type of IRI. Usually the IRIs are directed at specific grade levels, which allows a quick assessment of grade/real reading levels. However, some educators advise using only a single IRI for all grade levels, with the IRI designed to have higher difficulty. It is difficult to say which method is best; most literature on the subject simply reiterates the purpose and methods of IRI testing. Also, some IRIs miss the point of testing:
Other scholars in the field of literacy, as well, have suggested that main idea question types included in some IRIs were actually no more than "topic" questions that could be answered in one-word or simple phrase responses rather than full statements of the moral or underlying theme of a story, requiring the integration of selection content (Applegate et al., 2002; Duffelmeyer & Duffelmeyer, 1987, 1989; Schell & Hanna, 1981).
("A Critical Analysis..." readingrockets.org)
One major advantage to a single-IRI program is comparable scoring across all grade-levels; everyone is being tested on the same skills and subjects, so results can be easily compared. One major disadvantage is that higher grades may learn to trick the system, since they are being tested with the same methods; a different IRI each year ensures that students cannot easily cheat. In either case, the important aspect is the accurate assessment of the student's reading level.