San Antonio ISD:
https://www.saisd.net/admin/finance/...206-19-17.xlsx
(FYI: this link is a forced download .xls spreadsheet)
It doesn't have a specific category for Athletics, but I'm going to assume that athletics is some portion of the "co-curricular/extracurricular activities" line-item.
That would put the maximum athletics expenditures at $11,095,884 out of $594,638,217, a 1.87% share. The reality is probably that only a portion of that line-item is athletics related. Even if half that amount is athletics, that would still be .93% (still much higher than Austin's ISD).