I hope this is going to make sense:
My mom wants to do author visits to elementary schools. Because a previous health issue, her voice is sometimes loud and sometimes very quiet and she has a hard time getting people to hear her. It gets worse when she's nervous or stressed. The problem has been fixed and her voice is slowly improving, but it still comes and goes. Are there any cheap microphones that you could use in a classroom setting - so without much equipment? Maybe a mic with a speaker on the other end that you can just flip the switch and turn on, or something along those lines?