Touchscreens are often supplied with internal speakers that are inadequate for classroom use - the speakers are usually too small, the amplifier power is only 7 or 10 watts and the small eliptical speakers don't face the front so much of the sound is lost in the touchscreen casing and since speakers are directional it's important that they point towards the audience.

An answer to this is to use forward facing speakers at the right height - the height of your listeners ears. A soundbar fixed under the touchscreen is the best solution as the speakers can be large enough, the speakers face forward at the correct level and the sound output can be designed to suit young peoples hearing for voice at the correct sound level. Additional speakers can be wired to the rear of the classroom to ensure uniform sound levels ideally at 75dBA (15dB above normal speech)