Mason grew one inch between sixth grade and seventh grade. what type of developmental change is this?

It is called Quantitative developmental change.

Explanation:

Change is the permanent aspect in this world. Mothers feel happy when the child grows physically an inch taller or healthier than before.

Quantitative development change is the change which can be observed physically and can measured in term of units.

Quantitative development change is often connected to the physical growth which a child undergoes and it can by observed informally by the mothers. Nature and Nurture are the factors which contribute to the quantitative developmental change in a child.