How to use Joins followed by left outer join in ruby on rails?

I have the following database schema structure:

School
has_many :students

Students
has_many :books

Books
(has an attribute pages(integer))

The issue is I want a total of all the pages of a book a student has at the school level. But there is also a possibility that a student might not have any book.

I want to select the following rails query using ruby code and methods like joins and includes:

SELECT * FROM school INNER JOIN students ON students.school_id = schools.id LEFT OUTER JOIN books ON books.student_id = students.id

I have tried the following:

School.joins({:students => :books}).all

But this will not take into account those students who do not have any books. How to solve this?