We use the affordances of a supplemental digital literacy platform to study the dynamics of behavioral engagement and reading comprehension among middle-school students in remedial reading classes. All participating students (n = 315) were identified by their schools as needing additional reading support; 56% received special education services. They used the digital literacy platform designed using the Universal Design for Learning (UDL) framework for approximately 1 hr per week for an academic year. Embedded indicators of activity in the digital platform captured whether and how students engaged with available text-related activities. Higher levels of behavioral engagement were not associated with improved reading comprehension in the sample overall. An interaction effect indicated that students who started the year with lower reading comprehension skills were likely to benefit more from higher reading-related behaviors and more use of text-to-speech than those starting with relatively higher comprehension skills.