Example 1
A: You are a fine cook.
B: It's something I picked up/took up in school. Take up something - you make the decision to do whatever it is.
I took up golf when I was 11 years old.
Pick up something - to acquire a skill/knowledge without really deciding to do it or having to work/study/practice.
Example:
I live in Poland. I have NEVER studied the language, but I have picked it up.
So:
It's something I took up in school. - I decided to learn it/follow the course.
It's something I picked up in school. - I learned it whilst at school, but in a casual way.