[The_Reader_David]

Unfortunately, in most states teacher certification is teacher certification. It isn't specific to subject or discipline. If her district lost a few math teachers, she could well be in front of a math class the next year.

The math test requirement was doubtless put in precisely because math is the one subject they have trouble moving teachers into. (Mere literacy is enough to prepare an experienced teacher to change subjects--school science courses are appaulingly taxonomic any more, and shifting among the school analogs of humanities and social sciences basically means reading the text before the students do, but not so with math.)

[bannie]

Unfortunately, in most states teacher certification is teacher certification...If her district lost a few math teachers, she could well be in front of a math class the next year.

In my experiences, this is not possible. If one has a minor in a subject required, he/she may teach that class; but, I believe, he/she may not teach that course for an extended period without furthering his/her education in that subject area.