Hi Khan Academy! GRE Prep has long been requested here, but here's an unusual suggestion for GRE Quantitative Reasoning alone: GRE Math mastery-based course in your Math domain!
ETS, makers of the GRE, already recommend Khan Academy's Math courses for the Quantitative topics, and even have a dedicated page on their site for this. But there's no Official GRE Prep course on Khan Academy just yet.
So what if y'all curate GRE-relevant Math content into units and build a new mastery-based course? This is a lot like Get Ready Math courses, but rather a Math course with only the skills for GRE.
GRE takers can happily work through this course to 90% or more mastery, and teachers can integrate it into their classroom tools just like they do with any KA Math course from Algebra to Calculus and Statistics! And this isn't LSAT-style test prep at all - it's just another Math course on the engineering side, but content-wise it helps GRE takers!