## Tuesday, July 19, 2011

### Proofs in the classroom

Many of us have bad memories about proofs in the classroom and learned to switch off whenever they arrived.  After all, they were never assessed and the skill required always followed shortly after.   In texts today, the proofs are often missing and skills are instantly presented as the required content.

When writing assessment I tend to struggle with testing deep understanding vs trying to trick students into making mistakes.  I've read many external tests and they mainly use methods aimed at testing minute bits of content, "corners" of content areas rather than whether a topic is understood.  The wide splash of content that we are required to teach lends itself well to this method of assessment and it is quite easy to get a bell curve from it.

This is great for students that study hard and do lots of different types of questions.  It must be incredibly frustrating for naturally gifted mathematics students, the ones that enjoy delving into a new topic. I think this is where proofs need a more detailed treatment and where investigations in lower school can be repurposed.

The opportunity for delving into a topic is there for the picking.  Proofs for completing the square and Pythagoras' theorem are great ways of developing connections between geometric proofs and skills taught in classroom.  Developing conjectures about number patterns develops the idea of left hand side/right hand side of an equation and the setting up equations to solve problems.  Congruence, traversals of parallel lines and similarity are other topics that lend themselves well.

Having only taught upper school for awhile, it is interesting to see where the core ideas of geometric proof, exhaustion, counterexample, formal proof/conjecture/hypothesis and even induction can be introduced before year 11.  If 2C students can learn the idea of all but induction, there is little reason why we can't teach reasoning a little earlier.

Perhaps if they could reason more effectively they could then challenge their own results and complete investigations that developed into lasting learning events.