I give DDs sandwiches, or a boiled/poached eggs, beans on toast, home made soup. They are 7 and 3, they don't want another main meal!
I cook a main meal at lunchtime and have mine then, and heat it up for DH later, so I'm not doing two lots of dinners in the evening. So DDs always have the option of another hot meal if they want, but most often they want something light when they've had a school dinner. Particularly as some evenings DD1 has swimming or dancing so doesn't want something massive lying on her stomach before those activities. If it's shepherd's pie though DD1 will always have that!
Also I don't know what they are likely to be having for school dinner, so sometimes would end up duplicating it at home if I cooked a meal in the evening!
In the spring and summer they have sandwiches at lunch time and a cooked meal in the evening - so what's the difference there, nutritionally???
I tell you what the difference is for me as well. Since I've been eating a light meal with the kids at 5pm I've lost 9lbs. I'm a bit overweight, not obese, and need to lose a bit more. I don't want something heavy in the evening when it seems to be working not to! DDs are both exactly in the middle of the healthy BMI range, are doing well at school/nursery, have good concentration for their age, sleep well and their teeth are fine, so no, I'm not worried about their diet.
To me, paying £2.30 for a school dinner then making them a cooked meal in the evening is like having a dog and barking yourself...