Grade 13

Currently grade 13 is refered to as Ontario Academic Credit.

Ontario Academic Credit will be abolished in Ontario, in 2003, resulting in both grade 12 and 13 students applying to university at the same time. Ontario instituions are bracing themselves for an overcrowding of students.

I avoided grade 13 by moving to Massachusetts :-)

In Los Angeles, grade 13 is very often used as a reference to somebody's freshman year at Santa Monica College or sometimes West L.A. College (both of these are community colleges, who are not picky about who they allow admission into their school). Saying SMC (I will use SMC since it's the most common reference) as grade 13 is saying "I'm going to attend SMC immediately after high school". Describing SMC as grade 13 is not in any way a compliment. It is used is to show that SMC is not an advanced school but more of a another level of an LAUSD public high school. Since SMC is a community college and thus a "loser school" 13th grade is like saying you're repeating the 12th grade.