Bones are growing faster than muscles, and the skeletal structure begins to harden during this time. The onset of puberty occurs at an earlier age than in the past. Fifty percent of all girls will begin breast development at 11 years and menustration at 12 years. Boys may experience enlargement of the testes and penis around 12 years also. There is tremendous variation as to when sexual changes occur and how rapidly they take place.
Girls are usually taller and proportionately heavier than boys.
Boys are growing rapidly and have a more noticeable voice change than girls. The typical middle school student craves food since most of the students nutrients are used due to the rapid growth of body organs. Excessive perspiration occurs and sweat glands become active. The appearance of acne may cause students to feel sesitive towards their appearance. Endurance is not usually high due to the rapid growth spurt.