As students move in further classes, the books which they had used in that class is useless for upcoming students in that class. How can we use or dum those old books?
When my students cross their classes, then I take their old books so that I can use them to decorate my class. I cut out the pictures from those books then paste it on the bulletin board by creating a theme for my new students.
I think such a process will also help you. You can ask the teachers if they want those books for their solving or reading purpose or they can cut the picturers for project work or anything else…
You can keep the old books from which you can make your children’s project. In summer and winter vacations, children get a lot of homework and project work. Instead of looking for the written matter from internet, you can search from those books. As only little course changes in the higher class rest remain the same. Basics are the same which you can find from old books also, plus you can even cut and paste the pictures from those books instead of purchasing from the shop. This will save time and money as well.
This is my personal opinion that I used to take the books from my students so that, in case, if I have to refer any chapter or any question from the old book, so I can do that easily without any problem.
Maybe there are many teachers those who want to take the book from the students. You can ask the teacher directly, or your child can do the same thing.
You can offer your old books to the schools those who are underprivileged. Still, in India, there are schools which need donations and help from the government and society. Most of the people donate their old and used books so that children those who are unable to purchase the books can use those books. Or you can even give the books to the library of the school; they keep the books in case if anyone needs them.