I wonder if primary school children need to be exposed to decimals longer than one or two decimal places.?
For many children it takes several years for full understanding of the decimal number system to develop. Children need to work with decimal numbers that contain more than two decimal places to foster this understanding. They need to be able to see the general patterns of the endless base ten chain, not just a few isolated facts they can learn off by heart. There are many contexts (in measurement topics, for example) where such numbers are encountered and this should be encouraged in the primary school classroom.