Ninth grade spelling is basically a mixed bag of strengthening skills students hopefully picked up in their last eight years of education. They aren't kids anymore, and now is the time that they'll be acquiring specialized skill sets that will stay with them for the rest of their lives. In order to put those skill sets to use, they'll have to be able to adhere to a few conventions and know how to decode new words they encounter.
Ninth grade students will be expected to read more than they've ever read before. Every class will give them piles of things to read, and there's really no avoiding it. Students have to be able to understand what they read in order to be effective learners.
That sounds like a no-brainer, but many teachers encourage somewhat of a zombie approach to reading assignments. Read, read, read, they tell their students, but some teachers don't check that the students are doing the reading, and still more operate under the expectation that students are understanding everything book they peruse.
Every adult can remember nights in their rooms staring blankly at text books. You read three chapters, and then you can't remember anything at all. Hopefully, you read enough to pass the test, but wouldn't it have been nice to have absorbed more of the material?
That's where ninth grade spelling words come in. The more words students already know, combined with their ability to decode new words, the better they will retain the information they read.
In the ninth grade, students will read around one million words. Many of those words will be new. If students can't figure out what those words mean, they won't be learning the material. It's that simple.
There are some skills that need to be drilled by whatever means possible into the heads of students. Make a game out of learning and practicing the skills needed to be a successful high school student, and the benefits will be immeasurable.
The world is getting much bigger for ninth-graders. They cannot afford to be zombie learners anymore. Remembering word lists is something they'll have to do for the rest of their lives, but how they apply what they learn is something entirely different. Your job, or your responsibility, is to make sure your ninth-graders have the foundation on which they can build complex and abstract thought. Don't let them down.