Lily Withington, a teacher algebra at Deering High School in Portland, Maine, said this school year is the first in which she has a salary above $50,000. (Photo by Eesha Pendharkar/Maine Morning Star)Lily Withington started working in Portland schools seven years ago, but she didn’t make more than $50,000 until last year. As she unexpectedly found herself living alone after a breakup, responsible for double the rent, the raise was critical in al…