Is it necessary to have a hyphen in the following phrase?
Please my friends you are only hope for me at a last chance salon because my teacher he is not knowing answer.
You should add a hyphen whenever you're using a compound adjective for a noun that is being used as a single descriptor for the noun.
For example in the phrase you provided, graded-reading is a single descriptor all together for the noun books, and saying graded books, or reading books separately, won't make sense to imply what you mean. So, yes, you must use a hyphen there.
Read this article here.
If the books are about reading that is graded then yes, you can use a hyphen (probably what you need).
If the books are about reading and the books themselves are graded don't use a hyphen.
Also, check out ell.