isn't that what the scales under the bookcase in the club briefing room are for
Funny how everybody assumes that everybody flies a rented spamcan from a flying school...
Once you leave the school premises, it's a whole big wide and very threatening world out there
All of a sudden you have to do your own flight planning, check the tyre pressures, there is no tech log where to look up the fuel tank contents (which is of course completely useless, despite being common practice in the training scene), and you have to ask the passengers how much they weigh.
But seriously, if 1% excess over MTOW matters then something is very wrong; probably it means the plane is already 10% overweight.
I would be the last to suggest doing something illegal, and of course it is completely proper to demand sight of the POH for that particular plane, but some basic engineering common sense is called for here.