Beat sugar and butter at medium speed with an electric mixer until creamy. Add eggs, 1 at a time, beating until yellow disappears after each addition. Beat in lemon juice and vanilla.
Combine flour and baking soda in a small bowl; add to sugar mixture alternately with buttermilk, beginning and ending with flour mixture. Beat at medium speed just until blended after each addition. Pour batter into a greased and floured 13- x 9-inch pan.
Bake at 350° for 30 to 35 minutes or until a wooden pick inserted in center comes out clean. Cool in pan on a wire rack 10 minutes. Remove cake from pan to wire rack, and cool 45 minutes or until completely cool. Wrap in plastic wrap, and freeze 30 minutes. Place cake on a serving platter. Remove and reserve 1/4 cup Cream Cheese Frosting for decorations, and spread top and sides of cake evenly with remaining Cream Cheese Frosting. Top cake with Graduation Cake Decorations.