This study –which focuses on how secondary school students practice writing rules and use punctuations - aims to determine the students' errors in writing and punctuation. Within the scope of the study, there has been made an analysis of written narrative texts of 122 students who study in 5^th, 6^th, 7^th and 8t^h grades in Ankara. The study has been carried out in survey model as it aims to describe an existing situation. For this purpose, the visuals related to the concept of happiness have been shown and brainstorming technique is used. Afterwards, students are asked to write a text in any type they prefer. The writing rules and punctuation marks determined by the Turkish Language Institution are used in the evaluation of these texts obtained from students. Errors in students’ texts are analyzed for each grade level within two categories –namely writing rules errors and punctuation marks errors. Errors in the texts are explained by using percentage and frequency values. The errors detected by grade levels have been compared with the curriculum developed for the Turkish course and it is criticized to what degree learning goals are achieved. As a result of the study, it comes out that in all grade levels, students make more mistakes while applying writing rules. Under this category, it is observed that the most common errors in all grade levels are related to misspelling words and writing capital letters. When the errors regarding punctuations are examined, it becomes evident that students’ errors are related to usage of point and comma. As a result of these findings, it is concluded that writing rules and punctuations should be taught functionally to the students, and there is a need for detailed studies on writing and punctuation errors.