| 26 | NOIC Academy | Markham | Online/Site Based | Ontario Federation of Independent Schools | Visit |
| 48 | Town Centre Private Schools - High School | MARKHAM | Online/Site Based | Ontario Federation of Independent Schools | Visit |
| 70 | Canglory International Academy | Markham | Online/Site Based | Independent and Private School Forum | Visit |
| 153 | Across and Vertical Academy | Markham | Online Only | No Association Membership | — |
| 161 | AIS School | Markham | Online/Site Based | No Association Membership | Visit |
| 180 | Amberson College High School | Markham | Online/Site Based | No Association Membership | Visit |
| 181 | Amberson High School | Markham | Online/Site Based | No Association Membership | Visit |
| 235 | BrightMinds Academy International | Markham | Online/Site Based | Other | Visit |
| 250 | Cambridge Academy - Markham | Markham | Online/Site Based | No Association Membership | Visit |
| 259 | Canada Benson Academy - Markham | Markham | Online/Site Based | No Association Membership | Visit |
| 260 | Canada Benson Academy - Toronto | Markham | Online/Site Based | No Association Membership | Visit |
| 261 | Canada Cambridge Academy | Markham | Online/Site Based | No Association Membership | Visit |
| 267 | Canada International College | Markham | Online/Site Based | No Association Membership | Visit |
| 272 | Canada Nord Academy | Markham | Online/Site Based | No Association Membership | Visit |
| 276 | Canada Warden School | Markham | Site based only | No Association Membership | — |
| 283 | Canadian International Scholars School | Markham | Online/Site Based | No Association Membership | — |
| 341 | Deran Academy | Markham | Online/Site Based | No Association Membership | Visit |
| 348 | Duncan Academy, The | Markham | Online/Site Based | No Association Membership | Visit |
| 383 | Forest Heights School | Markham | Site based only | No Association Membership | — |
| 406 | Goldenlink Academy | Markham | Online/Site Based | No Association Membership | Visit |
| 423 | Hansen Academy | Markham | Online/Site Based | No Association Membership | — |
| 452 | Inspiration Private School | Markham | Site based only | No Association Membership | Visit |
| 468 | J Addison School | Markham | Site based only | No Association Membership | Visit |
| 481 | Kate Language School | Markham | Online/Site Based | No Association Membership | Visit |
| 510 | Lead Academy | Markham | Site based only | No Association Membership | Visit |
| 519 | Lorvale Academy | Markham | Online/Site Based | No Association Membership | Visit |
| 520 | Lotus Academy | Markham | Online/Site Based | No Association Membership | Visit |
| 558 | Merit College Online | Markham | Online Only | Other | — |
| 574 | Mosedale Secondary School | Markham | Online/Site Based | No Association Membership | Visit |
| 670 | Peoples Christian Academy | Markham | Site based only | Other | Visit |
| 679 | Queen's Elite Academy of Canada | Markham | Online/Site Based | No Association Membership | Visit |
| 692 | Rosedale Global High School | Markham | Online/Site Based | No Association Membership | Visit |
| 715 | Sharpminds Tutoring Inc. | Markham | Online/Site Based | No Association Membership | Visit |
| 721 | Silverwoods International School | Markham | Online/Site Based | No Association Membership | Visit |
| 777 | Toronto Elite School | Markham | Online/Site Based | No Association Membership | — |
| 781 | Toronto High School | Markham | Online/Site Based | No Association Membership | Visit |
| 785 | Toronto International Collegiate | Markham | Site based only | No Association Membership | Visit |
| 789 | Toronto Scholars' Collegiate | Markham | Online/Site Based | No Association Membership | Visit |
| 791 | Toronto Secondary School of Art | Markham | Site based only | No Association Membership | Visit |
| 794 | Toronto Trinity Collegiate | Markham | Online/Site Based | No Association Membership | Visit |
| 801 | Trillium School | Markham | Site based only | No Association Membership | Visit |
| 814 | Upper Crescent Academy | Markham | Online/Site Based | No Association Membership | — |
| 815 | Upper Hull Secondary School | Markham | Online Only | No Association Membership | Visit |
| 816 | Upper York School | Markham | Online/Site Based | No Association Membership | Visit |
| 820 | uStudy Learning Center | Markham | Site based only | No Association Membership | Visit |
| 825 | Vantage Academy | Markham | Online Only | No Association Membership | Visit |
| 828 | Veritas International School | Markham | Online/Site Based | No Association Membership | — |
| 829 | VES School | Markham | Online Only | No Association Membership | Visit |
| 835 | Visionary Academy | Markham | Online/Site Based | No Association Membership | — |
| 840 | Warwick Secondary School | Markham | Online/Site Based | No Association Membership | Visit |
| 845 | WeArt Academy | Markham | Site based only | No Association Membership | Visit |
| 848 | Wells Academy | Markham | Online Only | No Association Membership | Visit |
| 872 | YIP's Collegiate School | Markham | Online/Site Based | Other | Visit |
| 874 | York High School | Markham | Online/Site Based | No Association Membership | Visit |