ReadWorks.org is a website with free articles and questions that are organized by topic, grade, lexile, and reading strategy.
You need to register with the site in order to access the articles.
You can search articles by keyword, grade, lexile range, Domain, text type and skill/strategy type. The science related domains include: Earth & Space Science, Life Science, Physical Science, and Technology & Engineering. I have listed links to articles for Kindergarten and first grade in the science domains and informational text below. ***Note: there is a wide range of lexiles within the Kindergarten and First Grade Articles. Second grade teacher can also select these articles.
Kindergarten Articles
Earth and Space Science Domain
Life Science Domain
Physical Science Domain
Technology and Engineering Domain
First Grade Articles
Earth and Space Science Domain
Life Science Domain
Physical Science Domain
Technology and Engineering Domain