What reading level is the 21st Century Skills Library: Exploring Our Oceans series?

21st Century Skills Library: Exploring Our Oceans books are at a grades 4–5 reading level (average grade level 4.8), and HootRated recommends the series for ages 9–12. There are 2 books in the series.

What order should I read the 21st Century Skills Library: Exploring Our Oceans books?

Series numbers aren't available for most 21st Century Skills Library: Exploring Our Oceans books, so HootRated lists them by publication date: Jellyfish (2014); Lionfish (2015).

21st Century Skills Library: Exploring Our Oceans Books in Order

21st Century Skills Library: Exploring Our Oceans is a 2-book series by Susan Heinrichs Gray for ages 9–12, at a grades 4–5 reading level, with gentle to intense content (HootRated intensity 1–4 out of 5).

Books: 2; By publication date
Reading level: Grades 4–5; Average grade level 4.8
Recommended ages: Ages 9–12; From HootRated age ratings
Content intensity: Gentle to intense; HootRated 1–4 out of 5 · avg 2.5

21st Century Skills Library: Exploring Our Oceans Reading Order

Series numbers aren't available for most 21st Century Skills Library: Exploring Our Oceans books, so they're listed by publication date (oldest first).

#	Title	Reading Level	Ages	Content
1	Jellyfish 2014	Level 4-5	9-12	Intense
2	Lionfish 2015	Level 4-5	9-12	Gentle

Content Intensity Across the Series

Varies

Content intensity ranges from Gentle to Intense across the series.

First book Latest book

Series books grow with readers — but that's also the trap. Most series start at one reading level and one content intensity and drift upward over the course of the run. 21st Century Skills Library: Exploring Our Oceans (2 books by Susan Heinrichs Gray) lands at a grades 4–5 reading level, with average content intensity 2.5/5. Intensity varies from book to book, so check individual ratings in the list above.

The reading-order table above lists every book with per-volume reading level, age and intensity ratings so you can spot any escalation before it catches your reader off guard. For a deeper dive into how we score text difficulty vs. emotional weight separately — and why series readers especially benefit from that split — see our methodology page.

All 21st Century Skills Library: Exploring Our Oceans Books

Jellyfish

Susan Heinrichs Gray

Jellyfish

Susan Heinrichs Gray

Level 4-5 Intense

Lionfish

Susan Heinrichs Gray

Lionfish

Susan Heinrichs Gray

Level 4-5

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Questions about the 21st Century Skills Library: Exploring Our Oceans series

What reading level is the 21st Century Skills Library: Exploring Our Oceans series?: 21st Century Skills Library: Exploring Our Oceans books are at a grades 4–5 reading level (average grade level 4.8), and HootRated recommends the series for ages 9–12. There are 2 books in the series.
What order should I read the 21st Century Skills Library: Exploring Our Oceans books?: Series numbers aren't available for most 21st Century Skills Library: Exploring Our Oceans books, so HootRated lists them by publication date: Jellyfish (2014); Lionfish (2015).
What age is the 21st Century Skills Library: Exploring Our Oceans series appropriate for?: HootRated recommends 21st Century Skills Library: Exploring Our Oceans for ages 9–12. Content is gentle to intense (HootRated intensity 1–4 out of 5). Intensity varies from book to book, so check individual ratings in the list above.