A chemistry class expecting instructions from their professor instead got a very special message from his T.A. instead ... the one and only, Snoop Dogg.

Dr. Benny is the sharply-dressed teacher of Chem 60 at Los Angeles Pierce College, and on the first day of visual learning, he enlisted the rapper to send a very important message to his students ... read the syllabus!!

As for why, Snoop tells the class ... "The more you know, the further you go." Dr. Benny approves.

If first impressions are everything, you gotta think these college kids will be more inspired than ever to learn about elements and compounds.

After all, a Snoop Dogg Cameo doesn't come cheap at $750 a pop ... so Dr. Benny means business.