Introduction: Nowadays, schools typically manage their learning systems to focus on academic achievement for entrance to university. This may cause stress in grade 12 students. The objectives of this study were to determine the prevalence and related factors of stress among grade 12 students. Method: This was a cross-sectional study. A total of 657 grade 12 students were included. Data were collected from August to September 2015 through questionnaires consisting of demographic data, Suanprung Stress Test-20, and stress-related factors. Data were analyzed using descriptive statistics; frequency, percentage, mean and standard deviation. Multiple logistic regression was used to examine the relationship between stress and related factors. Result: There were 586 students completed the study (89.2%). Prevalence of stress among grade 12 students was 51.7%. Factors significantly related to stress included underlying diseases, inadequate expenses, household work, parents’ expectations for getting high-income jobs, too many assignments, lack of revision time, lack of guidance about university admission, and feelings of unfair treatment from teachers. Discussion and Conclusion: The prevalence of stress among this population was found to be high, which could be a cause for concern. It is necessary to develop an effective system to help these students. Moreover, schools should provide knowledge about time management, expense arrangement, and preparation for university admission. In addition, implement stress counseling services and prepare a system of referrals to relevant agencies may help to reduce and prevent stress. Key words: Stress, Grade 12 students
