Preheat oven to 350°. Cook macaroni according to package directions for al dente.
Meanwhile, in a large saucepan, heat butter over medium heat. Stir in flour, salt and pepper until smooth; gradually whisk in milk. Bring to a boil, stirring constantly; cook and stir 2-3 minutes or until thickened.
Reduce heat. Stir in 3 cups cheese and Worcestershire sauce until cheese is melted.
Drain macaroni; stir into sauce. Transfer to a greased 10-in. ovenproof skillet. Bake, uncovered, 20 minutes. Top with remaining cheese; sprinkle with paprika. Bake 5-10 minutes longer or until bubbly and cheese is melted.