LOTS OF HUNDREDS - Anne Kloack's kindergarten class at Allen Elementary School in Ann Arbor celebrated the 100th day of the school year Monday by studying the concept of the number 100. With 100 balloons decorating the classroom, students brought in 100 of various items - Valentine candies, baseball cards and paper hearts, among other items - to share. They used 100 napkins to wipe their hands after devouring 100 pieces of pizza. Kloack said the exercises help youngsters become acquainted with large numbers which are often hard to understand.