Is staring at a big, white wall during class making you feel dull? If you have ever walked past math teacher Mr. Kelley's room, you may have noticed how cheerful it is throughout the year. One thing that makes his classroom so much fun is the celebrity (名人) pictures on his front wall. Kelley's students have been writing to celebrities from across the nation asking for a photo and a few words of advice. 'It really takes a lot of time and money,' Kelley said. First, Kelley and his students make a list of all the celebrities to whom they want to write. Once a student picks a star, Kelley looks them up in his book of addresses to see if he can write to that person. Writing to the stars takes a lot of time because he has to personalize each letter, print them out, and address them. In the letter, Kelley asks the celebrity to send his classes a picture with some advice he or she would give to today's youth. Kelley takes up a collection in all of his classes and asks each student to contribute (捐) ft dollar to pay for the postage. Once Kelley mails off all the letters, the fun really begins. So far he has gotten back about 20 letters and pictures. 'The only thing that isn't cool is when the celebrity sends the picture back with no advice on it, which is my entire purpose in doing this,' said Kelley. When he gets at least three pictures returned, he lets his classes guess who the three stars are. He keeps score of how many celebrities each class has guessed. Jason Bryant, a student, said, 'It's become a contest(竞赛) between the classes to see who can guess the most stars, and it's really fun.' What is the text about?