You can double your sunday school every five years or less by helping classes to double every two years or less.
Quality is more important that quantity in our sunday school.
By quality I mean the quality of the lives we are producing. God has called us to make disciples, not converts. Nothing less than the production of fully mature disciples can be hailed as obedience to the great commission. Quantity is also important. Obedience to the great commission necessarily implies countable, graphable growth.