The best measure of a student's success at decoding is his oral reading fluency.  To assess a student's oral reading fluency is quite simple.  The teacher has the student read a short,  leveled passage out loud.  The teacher times the student for a minute and counts how many words she reads correctly. It's helpful to count errors as well. For a very reliable reading, it is a good to do 3 separate one-minute timings on different passages and select the middle score.  The QuickReads materials listed above are excellent for these timed readings.  Teachers may also use the DIBELS progress monitoring passages or comparable passages.  Norms are available to compare the child's performance with a national sample of students in the same grade.

The table below shows the median score for students at the end of first through third grades.
Words Correct Per Minute