Most decent boarding schools have a full varied range of food and alternate through popular choices. So maybe spaghetti hoops today, but perhaps veggie sausages yesterday and scrambled eggs tomorrow?
Also as it was just a taster day, there will be fewer students in school, therefore probably a smaller selection that average was provided. If you are still worried, contact the school and ask for a breakfast menu.
I'm going to be teaching in a boarding school in September, if you are interested, this is a selection of what the school is offering:
Every day: Cereals inc porridge, bread, toast and preserves, coffee, tea and juices, yoghurt and fruit
2 days a week: continental breakfast including pastries, cheeses and meats
Hot foods available on the remaining 4 days (not everything every day) include sausages, bacon, black pudding, eggs, french toast, beans, spaghetti hoops, hash browns and bubble and squeak.
On Sundays they have a brunch including full English, as well as weekly options such as omelettes, chocolate croissants, homemade sausage rolls, smoked haddock, baked brie wedges, chicken wings and paninis.
(unfortunately I will not be a live-in staff, so I will not get to sample this delicious food!)