"Levels of response" marking scheme (LORMS)

I knew there was a historian in me... Today, I was researching to find out more about social studies assessment in Singapore, in particular, the "levels of response" marking scheme... I found out that we use this to mark social studies essays, but why and how?

Nobody (on Google) seems to know... So I traced it back to its origins... It was designed for GCSE exam for history in the 1980s! Why? It was a way of differentiation by outcome! They wanted a means to use the same question to test students of various abilities and for that to show up through their answers!