I am specifically interested in instruments (e.g. questionnaires or scales) which primary school children could reasonably be expected to use with their peers.
Here are some papers. They are not all about primary school children but can give you some ideas. The Strength and Difficulties Questionnaire (SDQ) from Goodman was used in one paper:
Conference Paper Subgroups of problematic behavior among students of primary ...
Article The relation among achievement goals and academic achievemen...
Article Influence of Socio-Economic Status and Classroom Climate on ...
Article Statistics Anxiety among Postgraduate Students