I would aim for the parents evening to discuss any concerns and that opportunity to know exactly how the child is doing.
I am finding that school reports in secondary contain less information to how a pupil is progressing than primary reports, but because they have tests every term I think it's easier to know with the results how they may be struggling or not.
My dd primary reports had that bit of automatic writing but they did have personal detailed notes from the teacher which I apreciated.
In meetings I would discuss with the teacher what I was observing and listening from my dd on how she was doing in subjects, and the teachers would confirm it and give their input and advice.
I've been always very present in school material and study, working with dd, testing her knowledge, knowing the curriculum and going tro it with dd, asking questions after school, showing interest and excitement to hear her day, nothing strict, always in a fun way, like a routine thing, so after a while my dd would always keep me updated on how things were going at school, without me even asking. I also am attentive to her friendships and connections, it does really help to pinpoint how a child is doing and where is the struggle.