This National School in South Donegal had a renovation to the building back in 2011, not that long ago! However, while a number of the existing classrooms received refurbishment, the attention to the room acoustics were not part of the design. Along with refurbishment, NEW classrooms were built. Fantastic space given to the children, with vaulted ceilings giving an airy feel to the room, large windows letting in light, kitchen and  facilites area offset within the room. However, with this design of large open spaces with highly refective surfaces, you get high T_mf readings.
I dealt directly with the school principal Aoibheann Kelly. She had pointed out to me that not only did her teachers find it hard to teach and communicate with the junior infant students, one of her staff members was now suffering with vertigo and the HIGH frequencies reverberating in the new classrooms was causing her pain and discomfort. Mid frequencies and up ( 500 H_z through 2000, 4000 H_z ) are mainly the frequencies produced by children.

We produced an acoustic model based on the volume of the room and the various surface finishes wthin the room.
A T_mf of 3 seconds was calculated, this level is some 2.2 seconds above the design goal adopted for a Primary School Classroom as a retro-fit.
The desired T_mf for this space based on current regulations should be in the region of 0.8 seconds

The room surfaces comprised of the following: Ceiling - Plasterboard on Cavity and Painted : Walls - Plasterboard on Cavity and Painted : Double Glazed Units and Exit Door on One Wall : Floor - Industrial Vinyl :

Based on the layout of the room, we installed 28 m² of 50 mm thick abCOR Original White acoustic panels to the vaulted ceiling and 1 wall. 

We carried out a brief walk through video from a untreated classroom into an treated classroom so you can hear the difference for yourself.

Click on the picture below to watch the video.