Kellogg's "Corn Pops" was down at the bottom, rating only "fair."
"A one-cup serving has 12 grams of sugar and no fiber," said Klosz.
Kellogg's "Honey Smacks" and Post "Golden Crisp" also rated fair, with more than 50 percent sugar.
"Rice Krispies" didn't rate much higher. Even though it has a lot less sugar, it doesn't have any fiber.
"Fiber helps digestion and keeps you feeling full longer, so you might not gain as much weight," said Klosz.
Consumer Reports' nutritional ratings are based on the serving size listed on the box. To see how serving size compared to the amount kids actually pour themselves, testers asked 91 children to pour out a bowl of cereal. The amount poured was often a lot more than a serving size. That means kids can get a lot more sugar.
Consumer Reports found a few cereals that rated very good: "Cheerios," "Honey Nut Cheerios," "Kix," and "Life" received good marks.
"They're relatively low in sugar. They have some fiber. And they're a good source of iron and calcium," said Klosz.
Regular Cheerios earned top ratings for nutrition. It has only one gram of sugar per serving and a healthful three grams of fiber.