This starts with an Easy Reading component which includes brief sections for vocabulary-building with some pictures too. Continuing:
A Short Overview Of Science,
Classification,
Vertebrates,
Invertebrates,
Our Universe In Outer Space,
each of which is in English followed by Spanish to help any ESL / ELL students of Spanish background you have or may have later not only in regard to reading but also the science content area itself;
Next come longer reading sections also in English-Sp