One reading assessment that is used in my district is the STAR test. Most districts have purchased a site license for Renaissance Learning (aka Accelerated Reader). The STAR test is an assessment used by the Accelerated Reader program to develop the grade level of the reader and even assign a Lexile score based on their test performance. The student can take the STAR test as many times as necessary to allow the teacher to see growth throughout the year.

There is also a tool called Lexile Analyzer that will assess reading levels from K through 12.