In 2022, generative artificial intelligence (GenAI) chatbots like ChatGPT were released to the public and were rapidly embraced by many. Educational stakeholders are divided about whether to incorporate or ban chatbot usage in classrooms. Student engagement, a meta construct comprised of behavioral, cognitive, affective, and social components, is positively linked to academic achievement, student retention, and higher graduation rates. Self-determination theory proposes that the three basic psychological needs of autonomy, competence, and relatedness, when met, will increase a student's engagement. This explanatory sequential mixed methods study determined the impact of GenAI chatbots on student engagement levels in secondary students. The quantitative study examined secondary private school students in both control and intervention groups who completed the Writing Engagement Survey in a pretest-posttest design. The survey data were analyzed through univariate analyses of variance, and a qualitative focus group further discussed four emerging themes explaining the results. Quantitative results showed a statistically significant difference in posttest scores between groups in affective, behavioral, and overall engagement when using Gemini in writing. While the control group increased in engagement, the intervention group decreased, showing that chatbot usage lowered student engagement levels. Focus group participants identified chatbots as capable assistants that provide ideas but are inauthentic and individual experiences. Educational stakeholders will gain insight into incorporating chatbots as an educational tool instead of a replacement for teachers or peers. Ways to further investigate and improve student engagement levels are discussed. [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://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]