This is a situation that has been rumbling on since the earth cooled. @DreamW3aver and @GoldenCactus have both made valid point - it IS an odd way of explaining it, but they WILL also get people nitpicking too.
Many moons ago, the electrical department in which I was working introduced a £9.99 delivery charge. They chose to make this a separate, standalone fee. They didn't have to - they could have raised the price of the merchandise and said nothing, or if that was too much to add they could have added 50p to the price of everything we sold. But they didn't - they told people the retail price and told them how much to deliver it.
Now, while it wasn't uncommon for some customers to collect their purchases from our warehouse, I'd say 85% of them required delivery. Some customers didn't bat an eyelid, some moaned, and some tried to do all they could to collect their new fridge or washing machine or whatever, knowing full well it would never fit into the boot of your average saloon car. And all because of the principle of being told to pay for delivery.
You may note that a great deal of merchandise on Ebay now has P&P included without charge. I've been using Ebay for over 21 years, and remember only too well all the who-harr and drama some people made over what they were charge vs. the cost of the stamp on the parcel, with no thought to the time that had gone into preparing the parcel, and the cost of the packaging. Worse still, some folks bought things for a pittance, knowing full well in advance that the P&P was inflated to reflect a fair sale price. No wonder it's all included now.
Another example. A friend of mine runs a business providing a service. She has a few staff who work with her, thus her turnover is over the VAT threshold. She told me a she once quoted a new customer who told her he had no objection to paying the price, but on principle he refused to give the government a penny more of his money than he had to. He said had all of the fee quoted gone to my friend, he would have hired her on the spot, as this wasn't about the money, it was about who it went to.
I'm biased on this whole matter, because I really, really could not care who gets what - all I ever want to know is "what am I getting " and "who am I paying?". So in the case of the school meal fee here, if it were me I'd have no interest where the money went or why it was going up. But some people will ask, and then as soon as they start to explain you get people like the OP saying "well hang on, just a minute here...". The school won't be able to do right for doing wrong.
My question to you, OP, is "is £3.20 a good price for a school meal?", because I haven't a clue.