Hello,
I work for an adult school in California. We do a very complete set of intake assessments for each student: listening, speaking, reading, grammar and writing. Then each test is scored independently. Then the level of each student is determined.
Here in California, adult schools often use the CASAS reading tests. They are excellent. I also have used some CASAS listening tests, and I like them very much. You can find out more at the CASAS website:
https://www.casas.org/home/index.cfm
You will need to set boundaries (the line between a beginning student and an intermediate student, etc.).
Our intake assessments are very important and we can't live without them.