I was actually shocked to see the amount of people on here who were angry about someone bringing a phone to a public school.
When I had a phone in High School (around 2000-2002) most teachers didn't care unless someone was openly texting during class or didn't switch the phone into silent. Phones were technically against the rules at my school (officially because they "could be used to deal drugs") but few teachers enforced the rule as long as people were courteous and respectful. Most of us were able to handle ourselves reasonably and I only remember a few idiots' phones being taken off to the principal's office.
We don't need cell jammers at schools. We don't even need rules about using a phone in class. If a student is being discourteous to their teacher (i.e. obviously texting during class, or receiving multiple calls with ringtones) it's obvious that they're not just stupid, but they're also extremely disrespectful, and they should be dealt with accordingly.
A punishment for just having a phone that's off or on silent is stupid and insulting to people in that age group. If you never give kids the chance to learn how to conduct themselves as adults, then a lot of them will grow up and behave like children. Meaning, people who weren't allowed to have a phone in high school are probably the same idiots you hear with an annoying ringtone and a loud, squeaky voice two booths down at Chili's.
Also, texting doesn't cause bad grammar. From the first day I text messaged, I made an effort to type out coherent, complete sentences. Some people don't prefer to take the time, and that's okay, as long as they (like most people) know that texting is pretty much the only time and place when this is acceptable. Someone who turns in an essay that reads like a text message would have done something equally as stupid in the 70s. There are always people who can't write in school. It's disappointing to hear someone younger than me blame big bad Technology rather than just placing it on the individuals who deserve the blame.