My child's school did this too and confidence was a big issue until the children got use to this. I struggled to hide my horror when told the first result mark by my daughter! The second time she sat one and announced an appalling mark, I asked her how she felt about it before knowing how to reply!
The idea (so I was told) was to be able to judge how a child was thinking and working out answers. This would be (apparently) evident by how they went on to tackle more challenging work that they had not yet been taught. TBH she is flying at Maths, so perhaps it does work.