Tech teachers- how are you evaluating?

I’m a newer tech teacher but I also teach core subjects. It’s easy in core subjects to justify marks for the most part. But as a tech teacher I am struggling. I did some book work at the start of the semester and have some solid marks from that. But the rest as you know is mainly application. I usually give a rating out of 10 at the end of the week based on collaboration, initiative, being safe, cleaning up, time management etc.

But when a parent asks for “proof” of these marks, how can I explain it besides it’s my professional judgement? I have no kids failing; so I’m not too worried about parents coming at me. But I live in an area where parents may say “why are they only at an 85? Not a 95?” And I find it hard to explain my reasoning without any concrete proof.

Any tips ? I was thinking of some sort of tracking sheet or having the students hand in a self evaluation next semester.