We did wiring a plug as part of GCSE physics (bog standard combined/double science but 3 subjects were taught separately). Though of course not that much use now. I think my sister did washing symbols in GCSE textiles but she took that as an option.
I don't remember doing much useful in food technology TBH. I did finish it in year 9 but all I can remember is designing a new type of scone, making a fruit smoothie, and doing a baked potato with our own choice of filling. Not exactly rocket science even if you do mostly eat processed junk. I'd imagine most students can manage a jacket potato and beans! Yes if you can read you can follow a recipe, but lots of people don't.
Useful things IMO would be:
That pyramid/pie chart thing of how many portions of different foods, fruit/veg, carbs, protein, etc - not just that (as we definitely did that, but I can't remember it now) but also looking at how you can make up a day's or a week's meal plan to incorporate all of these things.
In fact, meal planning in general and how to use leftovers in another meal.
Really easy, basic cooking staples like soup/casseroles - things you can chuck anything into. How easy is it to make soup?? And cheap, filling and good for you. I took DS to the ex-inlaws the other day and XFIL was telling me they had a Czech student staying who was vegetarian and she had showed them how to make soup, and it was the first time he'd ever made soup in 58 years of his life.
Basic sauces - tomato sauce with chunky or pureed veg (pupil's choice), white sauce/cheese sauce, proper gravy(?)
4/4/4/2 sponge as someone said. I didn't know this was the basic sponge recipe until I was 21. I always thought cakes were difficult!
Looking at ingredients - what can be substituted if something is too expensive/fattening or the other way if you want to make something taste a bit nicer.
How to use herbs and spices and what they complement, to reduce reliance on packet mixes and salt.
Looking at food which is in season, how it tastes nicer and is cheaper at certain times of the year.
Then if they have time
:
How to bulk out meals with e.g. grated carrot, potatoes, lentils, without it tasting horrible.
Vegetarian food which doesn't rely on meat substitutes like quorn, or have an abundance of cheese. So many meat eaters are afraid of veggie food, but it's great!