Often, several reading tests must be used for a complete picture. Reading fluency and study skills are important. The best formal written expression tests have many flaws. Writing samples may be needed in addition to tests. It is useless simply to print a table of test scores and describe the scores in words.
Norms are worse than most people think.
Validity and reliability matter. Validity for specific purposes and reliability over realistic spans of time are rarely documented. Inadequate tests should be used only when they are absolutely necessary and the best existing for the purpose. Changes in circumstances can alter the need for special education. Stock, boilerplate recommendations are not much help.