Yes, tutoring centres and home school teachers can sign up students if schools are not participating. Please keep in mind that a certified teacher who is not related to the student will need to be arranged. Parents can proctor students, but students would be considered unofficial in this case.  The student must either be supervised in a school or location that the CMS has approved as an Official Competition Writing Centre (OCWC),  or must be supervised for the entirety of the exam by a proctor from a registered OCWC or a certified teacher under the ministry of education.