For Dl and D2 you must be cleared, along with your amature status.
Reason for getting it done early?
The Clearinghouse can take it's sweet time about processing. You don't want to have to be calling and scurrying around trying to "get 'er done " at the last minute. Junior and Senior year are stressful enough.
It really is just a matter of some basic information to be filled out, download some forms to give to your counselor that requests they send your transcripts - I believe one for Junior year, and then your final transcripts after graduation.
You are usually get a preliminary clearance first and then after your final transcript - your final clearance.
What this does basically is declare you academically eleigable (you have taken the proper core classes A-G in high school)
If you print the current requirement from the Clearinghouse, and have your student take this to the counselor, or better yet, do it together with your son to make sure he is taking the right classes.
It is really quite simple, the earlier you it though, you may be able to catch something that is missing or that he failed and take care of it.
You cannot take classes after he graduates to fullfil the requirements. However, there are ways to take a JC course, or do summer school after your Junior year (usually this is only offered for Failures.)
Just download the required courses and plan accordingly. If his plan from freshman year is to attend a four year college, he is probably on track already.