You are not required to attend a COURSE to get assessed.  If you are a current Level 2 ITRA technician, and you want to get assessed at Level 3, you can either have an assessor come to you and assess you on those skills, or you can come to them.  Or if you are not sure you have all the necessary skills mastered, you MAY take a Level 3 class and THEN assess.  It is totally up to you.