Background: Optimistic thinking is a facet of social-emotional learning linked to better mental health and problem-solving in children; however, few educational tools exist to improve this important aspect of self-awareness. Objective: To examine the effectiveness of an optimistic thinking tool with diverse students in an elementary school setting. Study hypotheses were that interacting with "Dream It! A Playbook to Spark Your Awesomeness" would improve children's understanding of and ability to dream about their futures and increase their optimistic thinking. Method: Using a non-randomized control group pretest-posttest design, fourth through sixth grade students (N=111) participated in a total of nine facilitated class sessions: N=60 children were assigned to the intervention group and N=51 children were in the control group. The majority of participants were female (56%) with a mean age of 10.21 years (SD=0.93). Mixed-methods pre- and post-intervention assessments were conducted at the first and last sessions with measures of dreaming (number and quality), optimistic thinking, hope, grit, and growth mindset. Results: Children in the intervention group demonstrated significant changes in dreaming and grit compared to control participants, with medium to large effects. Children's optimistic thinking, a vital component of social-emotional learning, significantly increased after interacting with an educational tool developed to teach them to dream about life goals. Conclusion: The present study offers evidence that the "Dream It! A Playbook to Spark Your Awesomeness" is feasible for facilitation in an elementary school setting and has the potential to improve key social-emotional learning outcomes for children.