When a three-year-old lesson-sharing website recruited teachers to share the work they had done adjusting their instruction to the new Common Core standards, New York City teachers were among those who took up the call.

BetterLesson’s new repository of Common Core-aligned lesson plans features 155 math lessons from five “master teachers” who work in New York City schools. Overall, the new site boasts 3,000 lessons in math and English from more than 130 teachers across the country.

The Common Core lesson library was born of a partnership between BetterLesson and the National Education Association, the nation’s largest teachers union. Like the smaller American Federation of Teachers, which includes the UFT in New York City, the NEA has complained that its members have been asked to revamp their instruction without getting the training or curriculum materials they need to do a good job. The new lesson plan library, which will grow weekly, aims to fill that gap.

Each lesson plan includes not only the standards it meets and the activities that students will do, but also videos of the teacher demonstrating and explaining his or her strategies and examples of student work.

For example, Marisa Laks, who teaches geometry at the Global Learning Collaborative, on the Upper West Side’s Brandeis campus, submitted a unit about “transformational geometry.” One lesson, in keeping with the Common Core’s emphasis on integrating literacy in all subjects, requires students to use a mirror to read the first verse of Lewis Carroll’s nonsense poem “Jabberwocky” to demonstrate the concept of reflection across the y-axis. The unit ends with a two day performance task that asks students to create a tessellating design that showcases both their knowledge of geometry and of Carroll’s “Alice in Wonderland.”

The other local master teachers are