I am planning a trip from YOW-YYZ-ATL this summer (likely on AC) and while conventional wisdom is to generally not check baggage, I am pretty sure I am going to end up doing so.

If I check a bag in YOW en route to ATL via YYZ, will it be searched by the TSA in YYZ or will it go straight through to ATL without their paws potentially sifting through my things? I know not to check anything remotely valuable (nor do I intend to) but I have heard countless stories of TSA employees snatching things from bags and I would rather not have to deal with that.