At what age should children start physical education classes?

Whenever they can!: PE time has been eroded from many public schools and it's a real shame! Being physically active and engaging in creative play is beneficial to a child. I believe all children should have structured quality recess/PE appropriate for their age. It actually helps them be better students! http://www.webmd.com/parenting/raising-fit-kids/move/parents-pe-questions?page=1