Where did your math educaton go all wrong?

If you take math exams from grade school to university where did It go wrong? For me grade 9 trig tripped me up. How far can you get 100% in a subject. Not limited to math. I could get straight 100% up to grade 7 if I took the exams today. Then It all breaks down. I forgot how to make colours from red, green , and blue that I learned in kindergarten. For math class it is built on the previous concept.