Becta are keen for schools to look at using Classroom Amplification systems in schools.
They give even sound across the room (teacher doesnt have to shout & strain their voice) so all children can hear.
It has been proven to improve results in the US.
Promethean now have a system (Activ Sound) & SMART do too.
I like the Redcat version.
PM me if you want any further info.