No one at the Lab Middle School for Collaborative Studies works harder than Stacey Isaacson, a seventh-grade English and social studies teacher. She is out the door of her Queens home by 6:15 a.m., takes the E train into Manhattan and is standing out front when the school doors are unlocked, at 7. Nights, she leaves her classroom at 5:30.

“She’s very dedicated,” said Tejal Bahtt, a fellow teacher. “She works way harder than I work. Yesterday I punched in at 7:10 and her time card was already there.”

Last year, when Ms. Isaacson was on maternity leave, she came in one full day a week for the entire school year for no pay and taught a peer leadership class.

Her principal, Megan Adams, has given her terrific reviews during the two and a half years Ms. Isaacson has been a teacher. “I know that this year had its moments of challenge  you always handled it with grace and presence,” the principal wrote on May 4, 2009. “You are a wonderful teacher.”