I'm not sure if it's because I have boys, it's hot here when school starts & will be for months to come, or they outgrow things at other times of the year, but we don't do the traditional back-to-school shopping I did as a kid.
For K, we did (#1) & will do (#2) a new backpack & lunchbox. Beyond that, I just make sure they don't need anything new, like shoes. I end up having to get stuff throughout the year so they usually don't need anything. Shorts season here is roughly April through October, so any new shorts or sandals they needed were long since bought.
And so far, they have zero interest in clothes or shoes.
Ds #1 is going into 2nd grade & he still has the same backpack he got for K. It's holding up & isn't babyish so....
Good luck & have fun!
Oh, & so far, we haven't needed to buy school supplies. I assume that varies by school & teacher, & will change when they're older.