Here are my suggestions:
"The issue of raising the number of years of required physical education classes is a controversial one. Some believe that physical education plays a very important part of high school overall experience where students learn valuable skills such as strategy, problem solving, and teamwork. Others believe that increasing physical education would take away more necessary time from academic learning and that physical education activities are extracurricular activities; thus, they should be done after the school day. After careful thought, I believe that the board should increase the physical education requirement to three years in order to benefit students health, teach students life skills, and help promote students psychological and mental benefits. You should mention the health aspect earlier in this opening statement.
Physical education benefits students overall health. Students build strength and endurance through physical education activities. Stretches done as part of the exercise routine help prevent unnecessary injuries. Regular exercise helps students build strong immune systems; therefore, it helps reduce the number of student absences due to sickness. Furthermore physical education also influences students long term health; it helps reduce chances of obesity, heart disease, high blood pressure, high cholesterol, and diabetes.
Next, physical education teaches students many valuable life skills such as strategy, problem solving, and cooperation. Many variety sport games offering through physical education classes teach students to work together toward a common goal. Furthermore, sport games teach students the basics of sportsmanships and that there is much more to sport games and activities than just winning and loosing. Sport requires training and mental and physical preparation, and it helps build self-confidence. Nice!
Lastly, physical education helps promote psychological and mental benefits. Exercise has shown to help reduce anxiety and depression. Exercise helps increase the blood flow to all parts of the body including the brain; thus, it helps improve memory and mental alertness.
In conclusion, physical education classes benefits students in many different ways. It helps improve student health, and through team sport games students learn necessary life skills such problem solving, strategy, and working together. And last but not least, exercise also has shown to improve memory and reduce anxiety. This is a hanging statement; it has appeared nowhere else in your essay. Do not introduce new information in your closing. Either place this somewhere earlier in your essay and give it its own paragraph, or remove the sentence completely. As a result, I believe that the board should increase the physical education requirement to three years."
Nice work! You've got excellent organization and structure. The flow is fluid and you use examples to support your assertions. Watch the inappropriate and incorrect use of commas, and figure out what you want to do about that hanging statement at the end. Good job!