Michael,

WELCOME TO THE AWS WELDING FORUM!!   And the world of welding as well.

Now, First off, you have no where near the pre-requisite number of years experience and or education to qualify to take the AWS CWI Certification Exams.  So, that lets that one out. 

Since you are going to welding school and are young, I would have thought they would have meant that you should do a welding coupon test to a particular code to see if you could be qualified as a welder.  That would open the door for you in finding work as you prepare for real world welding occupational employment.  Some school provide this though there is much question about it's value and merit.  It would be best to locate and use the services of a CWI to get Third Party Independent certification that can go with you to a certain degree though you will often still have to take a welding test at the place you are seeking employment.  That was probably what the instructor meant.  Not that you should try to become a CWI at this present moment, but that you should find one to take a welding test and be recognized as a qualified welder.

Just my two tin pennies worth.

Have a Great Day,  Brent

You are years away from a CWI.
I believe TWS will give you some type of certification that says you have done some test. This is not the certification you get when you complete the course work.
These certifications are only good to get you an opportunity to take a welding test. Pretty much what you get if you show up to fill out an application and have your hood and leathers with you. There is nothing magic about the certifications you get at welding schools. They are a piece of paper you hang on the wall or send to your momma to put on the wall. Some local companies in conjunction with the welding school or community college will accept the certificates for entry level positions.
But as a welder, you will never be done testing. That is just part of the trade. Even taking the CWI will require periodic retesting or additional training while you hold the certificate. The API certifications require retesting every six years to test your knowledge of the changes in the standards over the last six years.