Maze tasks have appealing properties as progress-monitoring tools, but there is a need for a thorough examination of the psychometric properties of Maze tasks among middle school students. We evaluated form effects, reliability, validity, and practice effects of Maze among students in Grades 6 through 8. We administered the same (familiar) and novel Maze passages for progress monitoring of a reading intervention among typical readers (n = 588), struggling readers receiving researcher-provided intervention (n = 471), and struggling readers not receiving intervention (n = 284). Form effects accounted for significant variance in Maze performance. Familiar passages had greater test-retest reliability than novel passages. Both administrative conditions had similar, moderate correlations (validity coefficients) with other measures of reading fluency and comprehension. There were also significant practice effects. Students who read the same passage showed steeper slopes in Maze performance than students who read different passages over time. Practice effects were influenced by beginning levels of reading comprehension and by intervention status.