It is well-established that being a self-regulated learner is beneficial academically, motivationally and is considered essential for productive life-long learning. Despite this, there is limited evidence examining how different measures of self-regulation for learning (SRL) relate to task performance for young students learning in digital contexts. This study investigated the relationships between different measures of SRL of elementary school students (N = 48, M[subscript age] = 10.75) while using a computer-based learning environment, and their association with task performance and teacher rating of student SRL ability. Results confirmed the most effective measure of SRL, in terms of its relationship with, and predictability of task performance, was a self-report written response, whereby students identified and explained known SRL strategies, such as how to plan, monitor or complete their work. Teacher ratings of their students' metacognitive capability were significantly correlated with task performance and with two self-report instruments: the Junior Metacognitive Awareness Inventory and the SRL written response. Associations between actual observed self-regulation behaviours in a computer-based learning environment, using Azevedo et al.'s coding framework and how students self-reported their knowledge and understanding about SRL, were weak. Observations of young students' SRL behaviours in computer-based learning environments were not significantly related to task performance. Better understanding of these relationships will help educators and researchers to know where they should focus their attention in terms of developing elementary school students' self-regulatory capabilities in digital contexts, as well as the reliability of self-report measures of SRL as relative to observations of self-regulation and task performance. Implications for teacher practice are also discussed.