I don't think people realise how bad Sensory Processing Disorder can be. I have three dc, two will eat anything. If you offered my youngest a bowl of ice cream or a bowl of broccoli he would eat the broccoli.
Ds1 will not eat food that 'touches' another food on his plate, no sauces or 'wet' food, no potatoes in any form, no sweets, cakes, or cereals. He will only eat one brand of chicken fingers or dippers, plain pasta, one brand/flavour of crisps, he will only drink milk or water. Sausages have to be Walls skinless if we give him 'normal' sausages we have to peel the skin away. He will try a small amount of sweetcorn or cold sliced red pepper (has to be red) he won't eat fruit at all.
This is a child who can sniff out a slice of (has to be orange) Warburtons bread from a bread line up. He lives on ham (has to be Tesco) sandwiches at school but no butter whatsoever. Add in the smells of the dining room and the noise and he struggles every single day, even his breakfast (toast) has to have no butter/spreads.
This is the reality of Autism/SPD. No amount of cajouling, forcing, or even begging will make him eat a food he can't. I say can't not won't. He will sit there and starve. Add in a severe nut allergy that triggers his already high anxiety.
We supplement his diet with vitamins and even those have to be a certain brand.
I'd like to know how private or Finnish schools would cater for him. Bear in mind he is very high functioning and thriving in mainstream.