What does "multiplication as scaling" mean?
Scaling means thinking of multiplication as resizing. Multiplying by a fraction less than 1 shrinks a number, multiplying by a fraction greater than 1 stretches it, and multiplying by 1 keeps it the same. Kids can predict the size of an answer before they calculate it.
How you probably learned it
You likely learned that "multiplying makes things bigger", which stops being true with fractions.
How your kid is learning it
Your kid compares without calculating: 3/4 × 12 must be less than 12, because you're taking only part of 12. 5/4 × 8 must be more than 8.
Why it matters
Scaling is a built-in answer check. If a kid multiplies 9/10 × 450 and gets something bigger than 450, they know something went wrong before looking at a single digit.
Where it shows up
Resizing photos, doubling or halving recipes, and map scales are all scaling. Later it becomes the foundation for ratios and percents.
