I think they may be, or at least they are visited by police officers. The 911 operators report any prank calls or calls that do not appear to be actual emergencies.
I was absolutely mortified 25 years ago when the police knocked on my door because my 8 year old and 6 year old called 911 from the extension in their brother's room. The police officer handled it beautifully. He told me every time the schools did their 911 training, they had a bunch of kids calling, either to test the system, hear how it worked or just because they thought it was "cool." He said some of it was pranks but he thought much of it was childish exploration. He asked to come in and talk to the boys, and he asked them why they called 911. The 8 year old said his teacher had told them to call if there was an emergency and gave them examples of emergencies. The teacher told them "be prepared and know exactly what you will do if there is an emergency." The 8 year old said he wanted to "be sure it worked in case he had an emergency." The officer told the boys that was very smart of them and then explained how 911 works from a police officer and emergency worker point of view and how busy they are answering life and death phone calls. He finished by telling the boys "Now you tested and you know the system works and I am there answering all requests for help, so promise me you will immediately call me at 911 if there is an emergency, But, unless there is an emergency, help me keep the phone lines open so we can protect people who need help."
I'm guessing his talk might have been different if he thought the circumstances warranted something more severe.