We feel its horses for courses. We have installed a whiteboard that actually sat on the floor as the Nursery teacher wanted the kids to have full access. It made it very difficult for her to use but she thought that the advantages out weighed the problems. Having said that, we have lowered existing installations to suite and raised them for others. Have you asked the staff what they would like? In lower KS1, I would think a bottom height of 40cm would be about right as it gives a good balance of usabillity for the kids and visibillity for the class.
Hello all BTW