CISAA - Conference of Independent Schools Athletic Association
Ontario Independent schools as defined by the Conference

COSSA - Central Ontario Secondary Schools Association
The counties of Haliburton, Northumberland, Hastings, Peterborough, Victoria, and PEI

CWOSSA - Central Western Ontario Secondary Schools Association
The counties of Bruce, Grey, Dufferin, Waterloo, Brant, Norfolk and Wellington

EOSSAA - Eastern Ontario Secondary Schools Athletic Association
The counties of Renfrew, Frontenac, Lanark, Leeds and Grenville, Stormont Dundas and Glengarry, Prescott and Russell, and Lennox and Addington

GBSSA - Georgian Bay Secondary Schools Association
The county of Simcoe, the districts of Muskoka and Parry Sound

GHAC - Golden Horseshoe Athletic Conference
The County of Halton and schools within the Hamilton-Wentworth Catholic District School Board

LOSSA - Lake Ontario Secondary Schools Association
The region of Durham plus Courtice Secondary School, Bowmanville High School, and St. Stephen's Secondary School in Bowmanville

NCSSAA - National Capital Secondary Schools Athletic Association
The city of Ottawa

NEOAA/AANEO - North Eastern Ontario Athletic Association/Association athlétique du nord-est de l'Ontario
The districts of Cochrane and Timiskaming

NOSSA - Northern Ontario Secondary Schools Association
The districts of Manitoulin, Sudbury, Algoma, Nipissing and the regional municipality of Sudbury

NWOSSAA - North Western Ontario Secondary Schools Athletic Association
The districts of Kenora, Rainy River, Thunder Bay and Patricia

ROPSSAA - Region of Peel Secondary Schools Athletic Association
The regional municipality of Peel and schools within the Peel District School Board and Dufferin-Peel Catholic District School Board.

SOSSA - Southern Ontario Secondary Schools Association
The regional municipality of Niagara South, the counties of Haldimand, Lincoln and the schools within the Hamilton-Wentworth District School Board

SWOSSAA - South Western Ontario Secondary Schools Athletic Association
The counties of Essex, Kent and Lambton

TDCAA - Toronto District College Athletic Association
Catholic high schools within the City of Toronto, and independent high schools within the boundaries of the City of Toronto not operated under the regular Ministry of Education Boards in the area, but not those which are members of the CISAA. Toronto District Secondary School Athletic Association TDSSAA Public high schools within the City of Toronto

TDSSAA - Toronto District Secondary Schools Athletic Association
Public high schools within the City of Toronto.

WOSSAA - Western Ontario Secondary Schools Athletic Association
The counties of Huron, Perth, Middlesex, Elgin and Oxfor

YRAA - York Region Athletic Association
The region of York