Locate on the test results your student's score in one subject matter such as reading.
Check the ISAT scale score cut points (an example of the scale is available here: http://www.isbe.state.il.us/assessment/pdfs/cut_points_09.pdf).
Find the label on the scale with the appropriate subject matter of reading, mathematics, science, or writing.
Beneath the subject heading, locate on the left side of the chart your student's grade level.
Move right on the chart until you reach the range that includes your child's score.
Move directly up from this score range to find the performance level. It will say either Academic Warning, Below Standards, Meets Standards, or Exceeds Standards.
Look up what that level means on the ISAT's performance definition sheet (available here: http://www.isbe.state.il.us/assessment/htmls/per_def.htm).