Learn NC and BetterLesson have sample lesson plans for subtraction with regrouping. The lesson plan from Learn NC meets first and second-grade Common Core Standards, and BetterLesson offers a lesson plan that introduces the concept.to second graders.
Learn NC suggests beginning the lesson with a review of subtraction without regrouping. Write a problem on the board, and ask volunteers to solve it using number cubes. After solving several of these, challenge the class with a problem that requires regrouping. Facilitate a discussion about possible ways to find the solution.
Use number cubes or base-10 blocks to represent each number, and demonstrate how a 10-block breaks apart into 10 one-unit blocks. Use the cubes to solve the problem, correctly notating the regrouping process as you work. Solve several problems using this method, allow volunteers to practice the technique at the front of the class, and then let students work in pairs to complete more regrouping problems using number cubes.
The sample lesson plan from BetterLesson uses a chant to introduce the concept of regrouping. Write "More on the top, No need to stop! More on the floor, Go next door and get 10 ones more!" on a chart or board at the front of the room, and ask the students to read it aloud. Write a subtraction problem that requires regrouping, such as "57-29," and ask students how to subtract nine from seven.
Repeat the chant again, and discuss the problem in terms of sharing pencils or candy to help students better relate. Demonstrate how to "go next door" to "neighbor five" and borrow 10 ones, and then allow students to work in small groups to distinguish between subtraction problems that do not require regrouping and those that do.