Not all of us get an access to a full fledged loudspeaker system, and the conventional voice amplification systems are not suitable for all situations - as not only are these PA systems bulky but also require complex setups.
A good speaker with microphone that has sufficient amplification can benefit a lot of people - be it teachers, yoga instructors, dance trainers, coaching classes faculty, or so on.
Below are some ideas:
Nefficar Voice Amplifier for Teachers is an ideal choice for all such needs and has a proven track record - you can see more details here