This is one of the first studies to evaluate the impact of computer-based individualized instruction in a developing country. We randomly assigned 1,528 students in grades 6-8 in 15 "model" public schools in Rajasthan, India who were using a computer-adaptive learning software to: a control group, in which they were only able to access the activities for their enrolled grade level; or a treatment group, in which they were able to access exercises appropriate for their performance level. After 9 months, computer-based individualized instruction had a null average effect on math achievement. However, treatment students with low initial performance outperformed their control counterparts by 0.22 standard deviations. Our results suggest that computer-based individualized instruction is most beneficial for low-performing students.