Preheat the oven to 350*.
Cook macaroni according to package directions.
While macaroni is cooking, melt butter or margarine in a large sauce pan over medium heat.
Stir in flour and salt and continue cooking/stirring until the mixture is bubbly.
Slowly add milk (about 1/2 cup at a time), stirring and heating to nearly a boil after each addition.
Simmer and stir the sauce until it thickens a bit (usually less than 5 minutes).
Add 1 1/2 cups shredded cheese, stirring until the cheese is melted.
Add cooked macaroni to cheese sauce, stirring until the macaroni is evenly coated.
Transfer to a 1 1/2 qt. baking dish sprayed with non-stick spray.
Top with remaining 1/2 cup cheese and bread crumbs.
Bake for 25 minutes or until cheese is melted and macaroni is heated through.