Risky behaviors (substance abuse, obesity, suicide, bullying, and others), many of which are indeed preventable, are common among high school students. The most important task in detecting, preventing, and intervening in risky behaviors in schools falls to the school guidance service and school psychological counselor. The main objective of this study is to determine the types and prevalence of risky behaviors observed among high school students and to analyze the practices performed by the school guidance service for such behaviors. This study was organized in accordance with the mixed research design for which qualitative and quantitative approaches were used together. In this context, quantitative (N1=566) and qualitative (N2=21) data collection processes were carried out with psychological counselors working in different types of high schools in 12 provinces. While statistical procedures were included for the quantitative data of the research, content analysis techniques were used for the qualitative data. The results showed smoking, peer bullying, cyberbullying, school dropout, obesity, delinquency, abuse, suicidal tendency and attempt, alcohol use, bonsai use, and other substance use as risky behaviors in high schools. The levels and frequency of these behaviors vary across school types. The preventive activities in the schools were generally based on informative seminars, and practical studies were limited. The research results also indicated that studies of risky behaviors were not sufficiently included in Ministry or school guidance framework programs. Furthermore, it was found that parents, teachers, and administrators gave limited support to the studies carried out within the scope of education and intervention for risky behaviors in schools. These results demonstrate that school psychological counselors encountered several personal, institutional, or legal obstacles in their studies on risky behaviors.