I wished they taught us the 'simple' stuff at secondary school as well. My teacher was more like "it's like that because it's defined like that". Thanks for fixing the gaps in the trains of my old teacher!
Ive been telling my students lately "Sometimes the easiest examples are the hardest examples". Which sounds weird, but I show them problems at a certain difficulty and they become accustom to that difficulty. Anything harder OR easier, it seems harder for them.