The aim of this study was to determine the levels of self-efficacy perceptions, STEM skill levels and computational thinking skills of the 6th, 7th and 8th grade students in the coding training. The study group consisted of 202 students studying in 6, 7 and 8 grades in a secondary school in Amasya city center. A mixed research design was used in the study. Qualitative data were collected by using semi-structured interview form, while the quantitative data of the study were collected by using Self-efficacy Perception Scale of Block Based Programming, Computational Thinking Ability Levels Scale and Basic STEM Skill Levels Scale. The quantitative data obtained were summarized as arithmetic mean, standard deviation, min, max, independent sample t, Anova, Pearson r correlation, regression, and qualitative data were analyzed by Nvivo and the following conclusions were reached. Secondary school students have low levels of self-efficacy perceptions for block-based coding education and have a medium level of computer skills. The students' self-efficacy perception levels for block-based coding education predicted 14% of the total variance together with their computational thinking skills and STEM skill level. Students have interest in robots and robot making.