I'm searching for great and unknown books with huge collections of hard and original problems for my students on High School Algebra or Olympiad level Algebra, related (but not limited) to factoring polynomials and identities.
What I need is a huge collection of hard and unseen problems in high school algebra, because unfortunately most of the problems in these books below are well-known to my students and cannot feed their hunger. My students are about 13 and 14, are really talented.
Problem Solving Strategies by Arthur Engel
101 Problems in Algebra by Titu Andreescu and Zuming Feng
Introduction to Algebra by Richard Rusczyk