So I've typed up in Excel all the Fourth Grade benchmarks from the book by Rebecca Rupp called "Home Learning Year by Year". Benchmarks are things a typical school kid "needs to know." But you be the judge of that.
Obviously, some stuff is important and leads to other things. There are other things on this list that you might just say, "sure, but we can hit that hard later on." And you would be fine. If you are teaching one child right now, it will be no problem to hit all these points. If you are like me and teaching 3 older kids and thinking about doing kindergarten with a 5.5-year-old soon while wrangling a younger one, you might choose to put some things off while focusing harder on others.
Other grades can be found here at the blog under the Blog Category of Benchmarks, as well as by grade.
Here are the benchmarks for Fourth Grade. As I'm putting them into Excel and uploading them to Google Docs. I'll be adding the others as fast as my fingers can type!
I suggest buying the book so you can also benefit from all the wonderful resources the author provides, as well as a longer description of each benchmark.