Correct. Also getting to 6th grade is generally defined as the the language skills needed to read/write news, most novels, contracts, information pamphlets, etc. The use of specialized language, such as technical lexicons, is where you get into higher grade levels of reading. There isn’t any universal standard as to what determines this, exactly. Many tests also work on being able to make sense of sentences that gradually become more, and more, obtuse. Their length, use of punctuation, tenses, and other technicalities, are increased until the person can no longer explain the sentence correctly. The problem with this is that it may be technically correct, but it is bad writing. If someone where to ace a test on some of this overly complex sentence structure, they would actually do worse for submitting it to a test of the skills on writing a sentence explaining something. So a lot of this lexical grading of reading level is nebulous, and results will vary from each person reviewing them, and exactly how they are performed.