"Fine!", said Carlos, "But I will leave my boxers on."
"Okay, suit yourself", replied Mr. Mendes. He waited Carlos finished taking his clothes off. He was an average sized boy, but stood about a foot shorter than Mr. Mendes. His body showed no development. With that, Mendes read a spell and watched to see the changes.
The changes were subtle at first. No one noticed anything until someone saw that Carlos was a bit taller than before. Carlos looked and saw the class slowly get smaller. Soon, his body started puberty. He felt a tingle in his crotch. He looked into his boxers and exclaimed, "Wow! I'm growing hair down there!" Black hair also began to grow around his ankles. His hands and feet grew out of proportion. The remaining baby fat Carlos had melted away. There was only a lean body left. Mr. Mendes glanced at how tall Carlos was getting. Carlos was now only half a foot shorter than the teacher (around 5'tall), and still growing. Carlos looked around the age of 13.
Then, the class watched in awe as Carlos experienced a growth spurt. His boxers were now very tight on him and failed to hide his growing penis, which was experiencing its own growth spurt. His limbs continued to stretch. Hair started to sprout everywhere; his leg hair thicken while softer hairs appeared on his arms. "ThIs Is sO cOOl" he shouted in cracked voice. He lifted his arms to cheer, timed perfectly for the class to see underarm hair grow underneath. Peach fuzz appeared on his face. Carlos continued to grow, meeting and soon surpassing Mr. Mendes' height. Suddenly, a ripping noise was heard as his boxers could no longer take the growth. "Oh no!" Carlos cried out in a deeper (but still thin reedy) voice as his privates were exposed. Everyone got to see the the pubic hair that had developed. His dick and balls were also bigger: his dick was about 4 or 5 inches long, his balls had grown a lot in size. Carlos was now about 16.
The growth in height started to slow down, but his muscles started developing. He didn't become extremely muscular, but defined. His leg muscles pushed out, his biceps enlarging. His chest heaved out, and his stomach formed some sort of four-pack. "I'm really big!" Carlos exclaimed. His voice had deepened to a manly tone. Carlos' height growth stopped, putting him at about six feet tall, only a little less than half a foot taller than Mr. Mendes. Then, hair continued to thicken all over his body. His leg hair could now be seen from the back of the classroom. His arms took a similar appearance. His pubic hair peaked, forming a trail in the middle of his torso, meeting the dark chest hair in the middle of his pecs. Carlos felt a warm sensation on his face as its peach fuzz was replaced by stubble, his jawline squaring off. The growth in his crotch slowed down, his penis was around seven inches, his balls the size of eggs. The changes stopped.
In the middle of the classroom, there stood a naked 18 year-old version of Carlos.