What statistical analysis would I run for the following example?

What statistical analysis would I run for the following example? A behavioral psychologist is interested in whether goal-setting activities can be applied successfully in public school classrooms. The psychologist randomly selects 30 middle-school students and randomly assigns them to three different groups that are assigned different levels of goal difficulty. The dependent variable is performance on a verbal-fluency test. Before the study, each student is given a general-ability test, whose scores are used to control for prior ability.