When a child is on daily report, there is usually a box for each lesson which has space for about 3 or 4 words. It is the give a v brief summary of the lesson or homework. It is not intended to provide the solution to the issue of why they are on report in the first place. It is so both parents and probably a Head of Year who is monitoring the child and who has probably set clear targets and expectations for improvement can see quickly how things are going.
So in all liklihood, the parent has already had a meeting with school before he daily report started and the child and their parent have a written plan or contract in place, outlining what the issues are and what steps are to be taken by both teachers and student to address them. The daily report is not like a full written report, but will be filled in at the end of the lesson in far less than 30 seconds. By nature it has to be brief - it is a tiny summary for tracking whatever the issues are.
Lazy might be an emotive word. However, when having to summarise a child's engagement with work, in a box where there is space for 4 words, which means you have to get to the point quickly, this is probably a useful and clear word.
No doubt, the teacher will have engaged with the child numerous times through the lesson and more feedback will be given. No doubt they will need to give more extensive feedback after perhaps a week or 2 weeks of daily report to the Head of Year, but it is simply not possible to give thorough feedback (involving lots of carefully chosen words and suggestions for improvement) on a sheet which probably has only 10 seconds available to it - and it's not intended for that, because it is just one part of a plan to help a child improve.
I wouldn't use lazy in a full, formal report. I might use it to summarise in one word, the approach of a child in an individual lesson.
To the parent who doesn't like the word, I would ask what role they are personally playing in keeping track of their child's work and helping him to meet the goals he has been set as part of his personal plan, which will have been created and include the daily report? He may have any number of extra needs, now rental response sounds defensive and makes me wonder how supportive they are of the school and how much of a role they are playing in helping him to meet his targets.