Prognostic statements are a standard component of assessments for adolescents at risk for language-learning disabilities, but there is limited evidence on the validity of prognostic indicators. In two studies, we collected measures of language ability and candidate prognostic indicators from adolescents age 12 to 13. We conducted an expository writing intervention. We observed relations between candidate prognostic measures and intervention response. In Study 1, a combination of compensatory and language ability measures better explained intervention gain than language ability measures alone. In Study 2, level of metacognitive awareness emerged as the prognostic indicator most associated with gain in holistic quality of expository essays. These exploratory data support the notion that selected compensatory ability measures aid in predicting gains from writing interventions for adolescents. The level of metacognitive awareness is a promising short-term prognostic indicator for adolescents who are candidates for interventions focused on ways of compensating for language ability weaknesses.