My source is wikipedia, whose source is in turn Indiana Department of Education. Not sure what the source of the discrepancy here is.
Edit: The school district's website gives the number as 30,000. Which seems a far too round number to be accurate, but adds to the ambiguity here.
Their own site says "more than 30,000" so it's safe to say that guy wasn't lying when he said that, he was just quoting the school district.
Following your link on Wikipedia shows a little less than that, but close enough.
His number may not be exact, but it's not a lie.
Indianapolis Public Schools (5385) | Indiana
inview.doe.in.gov