The Lesson Book is designed to be a one-semester course. There are almost 100 learning activities included. The first few lessons are easy, but as students work through the book, the activities take longer to complete. The last lesson actually provides exercises that can occupy a thoughtful person for a lifetime!
Once the student finishes the Lesson Book, they can use the software for their other studies. It will help them outline essays or research papers, prepare presentations, and analyze arguments. It is a tool students can take with them to college and beyond.
If your child is between grades 8-12, he or she should be able to work through the lessons on his or her own. It's probably a good idea, though, to review some of the child's completed work and offer feedback. (While many of the exercises have answers in the back of the book, others are more open-ended: that is, answers are not so much right or wrong as better or worse.) A one-page summary of the "Thought Tree Method" at the back of the book makes it relatively easy for a parent to get up to speed and provide useful feedback.
Theseus is an excellent supplement to any content-based curriculum. It teaches habits of mind that apply across the curriculum, and will deepen any course of study that calls for analysis and cogent expression.
Theseus provides a practical and engaging way to teach thinking skills while teaching content. In effect, it integrates logic and rhetoric instruction into any subject material you choose. TLS provides an exceptionally good introduction to practical logic, and in the process, teaches the structural aspects of effective rhetoric. It also works well as an introductory composition course, since it shows students how to organize their ideas prior to writing.