Understanding subtractions meanings and models with Dan Finkel @ Math For Love

Early Addition & Subtraction strategies (Kinder-1st)

In Kinder they learn to add and subtract within 10, and in 1st grade they learn to add and subtract within 20.

Later Addition & Subtraction strategies (2nd-3rd Grade)

In 2nd and 3rd, they learn fluency within 20 and to add and subtract within 100 and then 1,000.

Transition to the standard algorithm (4th Grade)