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High Five Bilingüe™ Magazine
Created for kids ages 2 - 6 years old, this 36-page magazine has 14 pages of stories, puzzles and activities entirely in Spanish, the same ones in English, and a few bilingual pages.
Muy Interesante Junior Mexico (Update: No longer available.)
Kindle version only. I'm going to take a guess here that the magazine is geared for kids up to 12 or 14 years old. According to Amazon, this magazine is created for kids who want to learn something different about the world every day in a fun way. It includes excellent information about science, technology, nature, history, art, space exploration, the human body, traditions and customs, and much more. The information is presented in a simple and entertaining format. It supports literacy habits and critical thinking in children.
Scholastic Spanish Classroom Magazines
These magazines are not geared toward specific grade levels, so much as language proficiency. You pick the level you are interested in and subscribe!