traditionally schools start after Labor day . I've taught in Phoenix and Cali as well as In. , Cali had the first experimental year round schools ( a joke), Phoenix was a wonderful experience as the schools were modern buildings equipped for the heat.
August in Indiana is NOT a fun month . IPS has tried to rig AC into 100 year old buildings w/o much success .

Schools are institutions to keep kids off the streets these days . I say this as graduation rates are right at 47%.