To help determine the grade level tests to administer, look first at the information you already have on the student. For instance, for a 4th grade student performing below 4th grade level, perhaps start testing them at the third grade level. Then, move up or down in grades and/or skill levels, depending on the results you get from testing. To compare test scores with students in the various grades levels, refer to the “Progress Monitor Scoring Guidelines.” The guidelines should give you an overall idea of where his skills vs. grade level lies. You may have to administer a few more measures, but eventually you will be able to determine his skill and grade level aptitude.
If the student is functioning at the 50th percentile in a lower grade, try administering a measure from the next grade up. In reading, the skill sets stair-step up in difficulty beginning with the fundamentals of reading: Letter Names, Phoneme Segmenting, Letter Sounds, and progressing up to the more difficult skills of Word Reading Fluency, Passage Reading Fluency, and the hardest of all, Proficient Reading. The student might possibly do better in higher grades of basic reading skills but need to drop down to lower grades on the more difficult skill sets. You are not only trying to determine where their knowledge lies, but also identify their ability to read and understand words and sentences.
For a student not functioning at their grade level, assess them at different grade levels. The goal will always be to get them back on their expected grade level as soon as possible and at the 50th percentile.