A reading tutor that listens to children read aloud should be able to detect fluency growth – not only in oral reading rate, but also in prosody. How sensitive can such detection be? We present an approach to detecting improved oral reading prosody in rereading a given text. We evaluate our method on data from 133 students ages 7-10 who used Project LISTEN?s Reading Tutor. We compare the sensitivity of our extracted features in detecting improvements. We use them to compare the magnitude of recency and learning effects. We find that features computed by correlating the student?s prosodic contours with those of an adult narration of the same text are generally not as sensitive to gains as features based solely on the student's speech. We also find that rereadings on the same day show greater improvement than those on later days: statistically reliable recency effects are almost twice as strong as learning effects for the same features.