Protective Ward is the first level focus spell from the Wizard's Abjuration school of magic.
Focus spells, like cantrips, automatically heighten to half your level, unless otherwise noted.
Protective Ward gives a +1 status bonus to AC, and radiates as an emanation, increasing area by 5 ft. every round it is sustained up to a 30 foot emanation.
As focus spell, how does Protective Ward heighten? The spell description (CRB p. 408) isn't clear.
Does the AC status bonus automatically scale or does the maximum size of the emanation increase? And at what levels does it heighten?
Or is it what it is, and the focus spell does not heighten?
All focus spells heighten automatically.
But Protective Ward doesn't gain any bonuses from being at a higher level. The AC bonus, range and duration all stay static. But the spell does still heighten, which is important for various abilities that interact with existing spells.
For spells that don't have any specific effect on heightening, it primarily helps for things like Dispel Magic that rely on counteracting (which is based on spell level).