[null and void]

But a non-driving teenager? I question the need and especially for an elementary student!

Oh, you mean the kids who can't drive themselves home when they misses the bus?

[ClearCase_guy]

In my experience, kids tend to "miss the bus" somewhat more frequently if they know that they can dial up Mom and get a ride home whenever they feel like it.

Kids who end up stranded some place have a tendency not to "miss the bus" next time.

Cell phones are often (not always) a crutch which enables bad behavior.