AIBU to force my son to eat school dinners?

[TakeawayAgain]

Hi all, I apologise if this gets long.

Backstory, my DS (5) is a very fussy eater. Having started on home made Annabel Karmel recipes from weaning, he will now only eat Birdseye chicken fingers and potato waffles for dinner, cheese, strawberries, grapes, banana at a push. No other meats, no veg, no pasta. He will eat chocolate and haribo of course!

We met a child dietician 6 months ago and we have a follow up booked for 18th October but not much has improved in that time, he will now try a new food, albeit the tiniest little mouthful, without making himself throw up but will very quickly decide that he doesn't like and sticks firm with that decision.

He started Reception two weeks ago and we decided that we would try to encourage him to eat food available at school (not have a packed lunch as he did in pre school) and would review this at half term having got feedback from the school and the dietician. We thought that at 5 he is old enough to understand that there are lots of different foods out there to try and that he could try to do with new friends eating theirs. This hasn't gone particularly well but not poorly enough for me to consider packed lunches earlier than half term. However, due to a very early hospital appointment, my DM took my DS to school yesterday and when it came to choosing lunch, he threw himself on the floor and a proper tantrum (for info, he is not this kind of child and has never done this with me). The school have mentioned that they don't think he is eating enough during the day (although he is eating crackers at afternoon break so there are some carbs going in), he has breakfast before school everyday and then his delightful chicken and waffle in the evenings.

I feel that the school are going to try to push us into switching to packed lunches asap but DH and I feel that this would be giving into DS' fussy eating and letting him regain control. I feel trapped in the middle because DH feels very strongly about this and I suspect he will think I've given in if I start to make packed lunches. However, I don't know if the school are right instead.

Would I be unreasonable to ask the school to continue supporting our decision on this until half term when we will review the situation? Funnily enough we had a huge breakthrough this week when DS sat with DH and ate an impressive amount of plain pasta so perhaps that's making this decision harder as there is a glimmer of progress.

If you made it to this point, thank you for reading! AIBU and what would you do?

Just wanted to add my little personal anecdote here.

My completely NT brother, aged about 5ish, suddenly decided he would eat nothing and I mean nothing, except bread and blackcurrant jam.
For over 2 years he point blank refused to eat anything else.
He would only drink weak tea or water.
Mum took him to several doctors, most of whom recommended starving him until he gave in.
When it became clear that DBro would rather pass out from hunger than eat anything else, mum gave in.

Took him to one final doctor, who shrugged his shoulders, said to just let him eat what he wanted, but he had to sit at the table with siblings/parents at mealtimes.

Eventually he started asking for a bit of mash, or ham and it got very gradually better from there.

That fussy, fussy git is now a chef, cooks amazing food, and will literally eat anything he can.

He travels the world looking for new recipes, and recently spent 2 months in Panama eating local cuisine.

There is hope!

Honestly DS was brilliant when being weaned, aged about 3ish suddenly went all beige food on me, but he's recently got much better.

So if I made spag bol, he'd only eat the the plain pasta, wolud refuse even grated cheese on it, but I'd put a bit of sauce at the side.
At some point he tried a bit of it, with no fuss, and it gradually built up from there.
Till the other night I realised he'd eaten all his sauce (loads of it!), smothered in grated cheese, but had only eaten a bit of the spaghetti!

He's swung the other way completely.

If there's anything to learn....it's that small children are strange, changeable creatures