I explain how the word "teen" in the "teen numbers" actually refers to ten. For example, fourteen means "four-ten", or ten plus four. Thinking of it that way, these "teen numbers" (thirteen, fourteen, fifteen, etc.) tie in neatly with place value.
We also practice with a hundred-chart, finding numbers ending in 5, whole tens, numbers in the 40s, and such.
Math Mammoth Place Value 1 — workbook for 1st grade math
Math Mammoth Grade 1 curriculum