This study aims to make a comparison of various lessons' mean exam scores achieved at the first, second, third and fourth grade by students who started elementary school at 60-66 months and those who started at or above 69 months as these students started the elementary school at the same time after an amendment in elementary education law in 2012. Screening method was employed as the study analyzes an existing situation. Target population of the study is 483 elementary school students attending the fourth grade at 27 elementary schools in Sincik district center of Adiyaman province in academic year 2015-2016. 249 of the students are male and 234 are females. The number of students who started elementary school between 60-66 months and attending the fourth grade is 74 while the number of students who started elementary school over 69 months and attending the fourth grade is 409. In order to ensure the equality of students in numbers, a total of 148 students were selected as sample group consisting of 74 students from each category. The findings were obtained by calculating the mean exam scores achieved by the students in Turkish, mathematics and life sciences at the first, second and third classes and in Turkish, mathematics, social sciences, physical sciences and English lessons at the first semester of fourth class. The exam scores of the students were obtained from e-school system of the Ministry of Education. It was concluded that there is a significant difference between the mean exam scores in Turkish, mathematics and life sciences at the first, second and third classes and in mathematics, social sciences, physical sciences and English lessons at the fourth class achieved by the students who started the elementary school at or above 69 months and those achieved by the students who started the elementary school at 60-66 months.