The current study focused on the development of a stretching exercise program for the improvement of the hamstring muscles, as part of the content of the "physical conditioning and health" unit of the first, second, third, and fourth courses of compulsory secondary education. The aim was to evaluate the efficacy of a stretching program on lower extremity range of motion (ROM) in students of compulsory secondary education. A total of 50 students belonging to two classes of second-year secondary education (weight=55.18 +/- 10.40 kg, height=157.68 +/- 7.00 cm, age =13.65 +/- 0.4 years) were divided into two groups (experimental group and control group). The experimental group performed hamstring stretches for 7 minutes during each physical education class over a full school term (9 months), two sessions per week (31 weeks, or 62 total sessions of Physical Education), with a stretch duration of 15 seconds, utilizing the active technique during warm-up and the passive technique during cool-down. The control group followed the standard class program of physical education classes. Hamstring flexibility was measured using the straight leg raise test before and after the program. The results demonstrate significant improvements in ROM for the experimental group (9 degrees), though the control group show worse results than initially (-2 degrees). For both groups, the initial and the final ROM between the right and left sides were similar. This study indicates that incorporating a stretching program as part of physical education classes increases the ROM of the hamstrings in students of compulsory secondary education.