I'm wondering whether it is acceptable to have older kids (I mean girls between 11 and 18 yr old) wear an apron at meals. I used to think that by 10 yr old, they would be able to eat perfectly cleanly but it seems that accidents still happen quite often. I don't mean they are doing a full mess of the meal, but still they may often end up with one or two little stains on their clothes. When my oldest was like 10 or 11, it was her idea to switch from the traditional child napkin tucked around the neck to a big cooking apron.
If it's the kid's idea to wear an apron at the table, then there's no reason why not. Moreover, if your oldest initiated the practice herself, then younger children may naturally follow suit. However, at some point, any child is going to bridle at an imposed restriction like this. (When a sixteen-year-old has a friend over for dinner, are they going to be willing to wear an apron at the table?)
If an older child objects, feeling that wearing something to keep their clothes from getting stained is infantilizing, I would not try to force it on them. Older children need to assert their independence, and they should be allowed a measure of personal responsibility. If you are worried about a teenager making a mess of their clothes, make the teen do their own laundry; a few times scrubbing out stains can convince them pretty quickly to be more careful.