I have always found it to be something that needs regular and repeated reinforcement.
If you have a lovely little poster number line display up on your wall, you can constantly refer back to and easily recall and reference your students' prior learning.
I have created a cute kids place value poster set for our classroom decor range and have also included a non-kid alternative should this be a bit too cutesy for your liking.
Simply print out the places (millions down to thousandths) that suit your grade. Use number cards or a dry-erase marker to model building different numbers and referencing the value of their place.
