Teacher candidates are NEVER to be  used as occasional (supply) or "on-call" teachers, nor are they to be  left alone in a classroom without a certified teacher present. This position is  supported by OSSTF/FEESO, the Ontario Teachers' Federation, the Ontario College of  Teachers, the Ontario Principals' Council, the Council of Directors of  Education and the Deans of Education.
  Under no circumstances should  teacher candidates be left alone in the classroom by associate teachers. The  associate teacher must be in the class or just outside of the class where they  can see/and/or hear what is happening. This is for the protection of the  associate teacher, who is legally responsible for the students in the class, as  well as that of the teacher candidate.
  Teacher candidates are not yet certified  teachers and as such may not have any legal protection should anything occur  which could involve charges of assault or negligence while they are alone with  a class. In addition, because teacher candidates are not yet dues-paying  members of OSSTF/FEESO, they do not yet have the right to representation or  legal advice from OSSTF/FEESO should an allegation of this nature be made  against them. Such an instance could result in the end of a teaching career  before it starts for the teacher candidate, as well as criminal action and/or  investigation by the Ontario College of Teachers against the associate teacher.
  That said, in the case of an  unforeseen extreme emergency, the teacher candidate should use common sense.  For example, if the associate teacher were to have a heart attack, the teacher  candidate should contact the school office to call an ambulance and should  supervise the students until a certified teacher or administrator arrives to  take over responsibility for the class.
 
So When Can I Start Teaching?
You will not be legally certified to  teach in the province of Ontario until you actually have your Certificate of  Qualification from the Ontario College of Teachers (OCT). In other words, having  an OCT registry number is not enough in itself. 
  Once classes end, the faculty of  education collects and processes the final marks and then sends the  recommendations and final transcripts to the Ontario College of Teachers. Once  the College has all of the required documents (including the final transcript),  it usually takes ten business days to review the file and certify the  individual. You will be able to check the status of your application in the OCT Members’ Area, and once it is posted,  print a copy of your Certificate of Qualification from the OCT Public Register called “Find a  Teacher”, while you are waiting for the paper certificate to arrive in the  mail. As soon as your Certificate of Qualification appears on the Public  Register, you are legally certified to teach. 
  A school board may offer you a  position contingent upon your receiving your Certificate of Qualification, but  normally that position cannot start until after you actually have that  document. If the start date of the position occurs before you receive your  Certificate of Qualification, the board could possibly apply to the Ministry of  Education for a “Letter of Permission” or allow you to teach under the  “Emergency” provision in the Education  Act BUT this can only happen if  there were no already qualified teachers who applied for the job or available  on the Occasional Teachers list to accept the job, and except in some very  specialized circumstances, this is rarely the case.  Furthermore, teaching in these circumstances  may also leave you vulnerable in that, in most cases, you are not paying union  dues and would therefore be without the protection of the union if something  untoward were to occur that would otherwise require union representation.
  
    
      What qualifications do I need to be eligible to teach in Ontario? 
       To be considered for employment as an elementary or secondary school teacher in a publicly-funded Ontario school, you must have a General or a Transitional Certificate of Qualification and Registration. The Ontario College of Teachers issues these certificates to qualified members.  | 
    
  
   
   
   
   
  
Legislation Related to Who Can Teach:
  
    
      
        | Education  Act section 1.(1) and section 262: | 
        
      
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        | 1.  (1) | 
        “teacher” means a member of the  Ontario College of Teachers; (“enseignant”) | 
        
      
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        262.  Except as otherwise provided in or under this  Act, no person shall be employed in an  elementary or secondary school to teach or to perform any duty for which  membership in the College is required under this Act unless the person is a  member of the Ontario College of Teachers. 1996, c. 12, s. 64 (11). | 
        
      
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        | Regulation  298 s. 21 “Appointment to Teach in the Case of an Emergency” (under the Education Act): | 
        
      
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        | 21. (1) | 
        Where no teacher is available, a board  may appoint, subject to section 22, a person who is not a teacher or a  temporary teacher. R.R.O. 1990, Reg. 298, s. 21 (1). | 
      
      
        | (2) | 
        A person appointed under subsection (1) shall  be 18 years of age or older and hold an Ontario secondary school diploma, a  secondary school graduation diploma or a secondary school honour graduation  diploma, or an equivalent to any of them. O. Reg. 29/08, s. 2. | 
      
      
        | (3) | 
        An appointment under this section is valid  for ten school days commencing with the day on which the person is appointed.  R.R.O. 1990, Reg. 298, s. 21 (3). | 
      
      
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        | Excerpt from Regulation  142/08 “Letters of Permission” (under the Education Act): | 
        
      
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        | 1.  (1) | 
        The Minister may grant to a board a  letter of permission for a period specified in the letter if, | 
      
      
        | (a) | 
        the director of education or secretary of the board or, in the case of a school  authority, the appropriate supervisory officer, submits to the Ministry an  application in the form required by the Minister, which shall include the  declaration of the person submitting the application that, | 
      
      
        | (iv) | 
        no  teacher has applied for the position or no teacher who has applied for the  position has accepted it, | 
      
      
        | (vi) | 
        the  individual is not and has never been a member of the Ontario College of  Teachers; | 
      
    
  
  
  The application form for a Letter of Permission (which is  contained in the Ministry  of Education’s Policy/Program Memorandum 147) requires the Director (or  designate), to sign off that “In addition, I declare that the board has  reviewed its list of occasional teachers, and has not identified an available  or willing candidate for the position.”