The Mathematics Assessment Project (MAP) has created lesson plans for high school lessons in maths based around formative assessment. They make the following remark about marking students' work in this teacher guide for a lesson about substitution.
We suggest that you do not score students’ work. The research shows that this will be counter-productive, as it will encourage students to compare their scores and distract their attention from what they can do to improve their mathematics.`
I would like references to research that supports this claim.