In small bowl, stir sugar and yeast into 1/2 cup warm water (105 to 115 degrees F); let stand until yeast mixture foams, about 5 minutes.
In large bowl, combine barley cereal, cornmeal, salt, and 4 cups flour. With wooden spoon, stir in yeast mixture and 2 1/2 cups warm water (105 to 115 degrees F) until combined. With floured hands, shape dough into a ball in bowl.
Cover bowl with plastic wrap and let rise in warm place (80 to 85 degrees F) until doubled, about 1 hour.
Punch down dough and turn onto well-floured surface. Knead dough until smooth, about 5 minutes, working in more flour (about 3/4 cup) as necessary while kneading.
Grease large cookie sheet. Cut dough in half and shape each half into a 6-inch round. Coat each round with flour; place on cookie sheet. Cover loaves with towel and let rise in warm place until doubled, about 1 hour.
Preheat oven to 400 degrees F. Bake loaves until golden brown, a total of about 35 minutes, using spray bottle to spritz loaves with water after first 5 minutes of baking, and again 10 minutes later. Cool on wire racks.