If you're looking for a way to phrase something as diplomatically as possible while still getting your point across, these may help!
https://www.tes.co.uk/teaching-resource/comments-for-report-writing-3013164 - Suitable for Infants
http://www.educationworld.com/a_curr/profdev/profdev148.shtml
http://www.teachercreated.com/blog/pics/Report%20Card%20Comments.pdf
https://www.twinkl.ie/resource/roi-c-012-irish-report-bank-of-statements
https://www.tes.co.uk/teaching-resource/comments-for-report-writing-3013164 - Suitable for Infants
http://www.educationworld.com/a_curr/profdev/profdev148.shtml
http://www.teachercreated.com/blog/pics/Report%20Card%20Comments.pdf
https://www.twinkl.ie/resource/roi-c-012-irish-report-bank-of-statements