Why “reading level” is not one number
Reading involves word recognition, fluency, vocabulary, comprehension, background knowledge, and the demands of a particular text. A timed oral sample observes only some of those parts.
What you can record at home
Use grade only as a starting point
A school grade can help choose an initial passage, but it should not become the result. If the passage is clearly frustrating or too easy, record that observation and choose a more appropriate next sample.
When to ask for a fuller assessment
Talk with a teacher, reading specialist, pediatrician, or another qualified professional when reading remains distressing, progress concerns persist, or you need formal evaluation and instructional guidance.
For a narrow, repeatable starting point, follow the parent-guided reading fluency check.