Does the number of creatures affected by Sculpt Spells increase with upcasting the spell?

As a level 2 Evocation Wizard, the School allows you to sculpt spells around allies, up to 1 + the spell’s level, allowing them to avoid the effects of the spell. Certain spells, such as Thunderwave, allow you to cast them using a higher level spell slot.

My question is: which level do you use when calculating the amount of allies that can dodge your spell? The actual spell level (for Thunderwave, this is 2), or the level of the spell slot you use when casting (which effectively raises the level of the spell)?