The idea that goodness is destroyed by cooking is a bit of a myth. The vitamins and minerals in carrots are actually made more accessible by cooking. Some vitamins ie vitamin C are destroyed by heat but many aren't.
Some fruit might be 3 years old but that is very rare - the more perishable fruits strawberries, blueberries, mandarins etc just can't be stored that long. If you buy from the farmer's markets the fruit is very fresh.
We only need about 3 serves of protien a day. Protien is found in an amazing array of foods - cheese is quite protien rich and ful of calcium too. Also mushrooms, nuts.
There is a subtle but important differance between reducing the amount of calcium available and maing it unavailable. A child will get less calcium from chocolate milk than straight but far more than from no milk at all.
Vitamin C increases iron absorbtion so if you have a steak eat drink an OJ at the same time or eat some strawberries afterwards. Calcium reduces iron absorbtion so if iron is a concern don't drink milk after your steak. Or have lasagne or cheesey sauces with meat.

TBH I'm not convinced that your teacher is as well informed as she should be.