Yesterday I bought 500g of mince. I used 5 tins of the cheapest supermarket chopped tomatoes I could find. I chopped a couple of onions, celery garlic, tomato purée, salt and pepper and cheap own brand dried herbs, with decent olive oil as the base mix.
I also then made about 3/4 pint of white/bechamel (butter, flour whole milk, salt, a little crushed garlic, pepper, bay leaf, mace).
I used fresh chopped parsley and basil for some, and I also used 2 cans kidney beans and a can of green lentils, some fresh coriander and ground cumin, coriander, chilli flakes, salt and pepper for a larger portion.
Using all of the above, I made:
1 large lasagne (serves 4 generously)
1 small lasagne (serves 1 generously)
6 portions of chilli (with rice cooked and put in freezer)
3 portions of spaghetti bolognaise sauce.
The mince was 20% fat and the pasta I used was the cheapest stuff I normally buy in the supermarket.
The ingredients I bought cost me £20 plus the stuff I already had (2 cans kidney beans, pasta/lasagne sheets - but all the cheapest versions).
I also made 12 portions of soup using chicken bone stock made with cheapest carrots/onion/potato etc and made chicken and veg soup in the stock pot (using the cheapest skin on/bone on chicken thighs I could find) and two cheap tinned tomatoes and cheap back bacon to make tomato, bacon and red lentil soup.
I think that in total, cost me a tenner.
Of course it relies on you having a few basics and it really depends on what your kids like / none of this would've worked for my eldest as he's autistic and very good averse, but I cook rarely for him now so this works for my other two teens. I hate food planning and although im a decent cook, really struggle with cooking drudgery as well as the cost thing. I tested all this stuff out yesterday do this is all recent, and doable provided you have a head start with some of the basics (pasta/seasoning/rice etc)