Textbook options for critical thinking at different levels

 Kindergarten-Grade 2:

• "Curious Kids' Activity Book: For Critical Thinkers" by Elizabeth Verdick and Marjorie Lisovskis
• "Big Thoughts for Little Thinkers" series by Joey Allen (four-book series covering theology, philosophy, and apologetics for kids)

Grade 3-5:

• "Mind Benders" series by Anita Harnadek (a series of books with puzzles and games to develop critical thinking skills)
• "Critical Thinking Detective: Vocabulary Book 1" by Michael Baker
• "The Kids' Guide to Critical Thinking: Turning Questions into Opportunities" by Rebecca Wingard-Nelson

Grade 6-8:

• "The Art of Reasoning" by David Kelley
• "Thinking Critically" by John Chaffee
• "Argumentation and Critical Decision Making" by Richard Andrews and Laura Jackson

Grade 9-12:

• "The Art of Reasoning: An Introduction to Logic and Critical Thinking" by David Kelley
• "Critical Thinking: An Introduction" by Alec Fisher
• "Thinking Critically About Ethical Issues" by Vincent Ruggiero

Note that these are just some possible textbook options and there may be others that suit a particular teacher's or school's needs better.