* Country: School systems in different countries have different calendars.
* State/Province: Even within a country, individual states or provinces set their own school calendars.
* District: Individual school districts can also have slightly different start dates.
* School Level: Elementary, middle, and high schools might have different start dates within the same district.
To find out when school started in 2015, you need to specify the location (country, state/province, and ideally the specific school district).