What school taught me

Primary school:
Pencils are used in all of our homework. At this point, mistakes done can be easily erased.

Secondary school:
Upgrade to pen. While we relish the feeling of being adult-like, any writing mistakes done at this stage cannot be done away with an eraser. You can try, but trust me, you are going to end with a huge hole in your book.

College and Uni:
Oh curse the oral exams and presentations! This stage of education teaches us that gift of the gab is important. And that any words you've said cannot be taken back. So, be careful of what you say.