There are many reasons why cell phones should not be allowed in the classroom. Distractions
When a child is in school, his or her purpose there is to learn, whether it be about Columbus sailing the ocean blue or about how electricity works. Young people are more easily distracted than their elders because they tend to have shorter attention spans. If they become bored with the class material, it doesn't take much for them to take out a Motorola Razar to play some cell phone games. How can you expect a teen to absorb all that knowledge if they're not even paying attention.
Obviously, kids won't be able to take out their cell phones and talk to one another in the classroom during an exam, but the concept of "passing notes" has stepped into the age of technology, thanks to the advent of text messages. These can be sent quite discretely while in the classroom. Taking it one step further, a student can excuse himself to go to the washroom, only to use that time to send text messages and leave voice mails. You also have to bear in mind that cell phones are advancing and improving faster than ever. Certain smart phones can surf the Web (looking for test answers), others have advanced calculators, and depending on the software, it may even be able to run custom applications. The possibilities for cheating and copying are literally limitless, and thus another con of cell phones in school.