ds is year 9 and dd is year 7.
I guess I get as involved as I need to be. So initially there was a lot of 'have you got any homework?' I would occasionally check the planner.
I would remove phone and send ds off to do his in year 7/8, but now in year 9 he is totally responsible.
There were a few projects that ds asked for help with, and still, very occasionally moments where he gets stuck and we support.
We did notice that his French was dire, and we bribed him to use dualingo for 4 months to practice and that helped enormously.
School told us about a long English project in year 8 that needed planning and we pushed him to make sure one item was done each week, and not all left to the end.
dd in year 7 is almost entirely independant. This is partly because she does a lot of hers at lunchtime, and has very little in the evenings.
She did get a big art project, and we sat down together and worked out how she was going to structure it.
Their schools are quick to pick up on homework not handed in, so we would know if there was a problem.
But I think they are both unusual in being quite independant. I would have supported and helped more if they wanted it. Most of the help I see as necessary is providing a time and a place, and letting them know we care about it, and are there if they need it. I have almost never helped with content. I think the only time was when ds was struggling to find the right information online, and so we searched together and I helped him to work out what fitted the criteria. And maybe the occasional maths question for dh.
Exams is the time we have ha dto be more involved, and insist on revision, and enforce phone free revision times.