I've already given my answer to DS on this already, but interested on views.
DS 14, year 10, doesn't often go out in the evening but today he's unusually at his GF's house and just messaged to ask what time he should come home. We live at the 'rougher' end of a 'naice' area but still low crime and relatively safe. He has a 5-10 minute (max) walk home - mainly along a main road, but he has to pass a very slightly dodgy parade of shops where occasionally there are groups of older teens/young 20s hanging out being a bit noisy/cocky.
What's a reasonable curfew?