This manuscript style dissertation investigates the impact of a brief positive psychology group intervention on both wellbeing and academic achievement among adolescents. Two experimental research studies were conducted to address this. Participants from a local high school engaged in a brief small group positive psychology intervention in both studies. The first study focused on wellbeing outcomes. Wellbeing was assessed using self-report questionnaires measuring depression, anxiety, stress, hope, school connection, and overall wellbeing. Utilizing a multiple baseline design with each participant serving as their own control group, changes between baseline to intervention were measured. Results indicated reductions in anxiety and stress for most participants and limited improvements of wellbeing, hope and school connection for some participants. This study highlights the potential of school counseling group interventions to positively impact adolescent wellbeing. The second study focused on factors related to academic achievement including attendance, grades, work completion, and office discipline referrals. Participants were grouped together for analysis and data revealed limited success of the intervention on academic factors. When separated into individuals, a reduction in office discipline referrals was seen for most students. Overall, these studies provide valuable insights into the effectiveness of school counseling group interventions on both wellbeing and academic achievement for adolescent populations. The findings contribute to the literature on positive psychology interventions in school settings and have practical implications for school counselors and educators aiming to support the holistic development of secondary students. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]