I have strong opinions about this. Earlier this year we had a tornado warning in my area that lasted for quite some time. We had several tornadoes touch down and one person was killed by flying debris.
I have two kids in middle school, both who carry cell phones. Our school's policy is no cell phone use during the school day unless it's academic-related (there are not enough computers for every child to use one), no texting or talking during the day. They have told us time and time again, "your child doesn't need a cell phone. If there's an emergency, we will let you know what's going on. You can call the office to reach your child in an emergency."
Well, when the emergency happened all of that went out the window. The tornado warnings started right as they released the buses. They e-mailed all parents and said they were taking the kids back to the school to shelter in place. About 15 minutes later, I get a text from my son saying, "I don't know where we're going - we just passed the school". I call the main office, no answer. 20 minutes later, my son texts me and says that they took him and his brother to a completely different school a few miles away, and that he's in a gym with 1000 other people. I know that school - the gym is in the middle of an open field and is not a storm shelter. But it appears not all of his friends are there - he says some kids were taken to a different school but he doesn't know where. Still no word from the school - I'm getting texts from my friends (whose kids don't have cell phones) seeing if my boys can try to find out if other kids are there. Nobody knows what's happening.
Ultimately, I ended up driving to the school and removing my boys from that situation, and taking us home to our (much, much safer) basement. They ended up keeping the majority of the kids for four hours (until 7 pm) with no notification to parents. Other moms that I knew were frantic, and it was rational because they literally had no idea where their kids were. The only reason I did was that my boys had cell phones and let me know. I'm grateful, because had a tornado hit that building there would have been a lot of kids who had died.
So my answer is yes - I want my kids to have cell phones, because I don't trust the school to keep its promise in making it not necessary for them to have one.