The aim of this study is to develop a valid and reliable instrument to assess why physics courses are perceived as one of the most difficult courses among high school students and to investigate the reasons why students have difficulty in learning physics through this scale. This study includes the development and validation studies of the Difficulty in Learning Physics (DiLP-S) Scale for High School Students. A draft scale study was applied to a group of 1021 high school students. At the end of the study, a scale consisting of 25 items (a = 0.921) was developed representing 52.372% of the total variance. Based on exploratory factor analysis, it has been observed that the scale was grouped under three factors and the factors were respectively, "Teacher" (ten items, a = 0.892), "Content" (ten items, a = 0.853) and "Student" (five items, a = 0.851). The values obtained from the results of Confirmatory Factor Analysis (Chi-Square = 720.53 (p = 0.00), df = 272, p-value = 0.00000; RMSEA = 0.064 and CFI = 0.97), put forward a good fit between the hypothesized theoretical model and the empirical data. According to results, students emphasize mostly the content of the physics course as a reason for perceiving it as difficult. Then, students, and lastly the teachers follow it. When the scale's score means are compared according to the students' class levels, it was found out that the 9th and the 11th grade students had more difficulty in learning the physics course than the 10th graders. When the students' academic success in the physics course and the scale scores were compared, there was not a significant difference. Namely, whether they are successful or not, the students perceive the physics course to be difficult.