not public schools....they perpetuate a cycle of misuse of funds and lies.
Ontario? Call the health unit where you live. Ask if they have a form online you can print. Fill it out. In our area it needs to be sworn in front of someone - so I take it to the township office and pay them 10$ to stamp/sign it. I then send a copy to the health unit (keep a copy - they lost mine!!!) and give a copy to the school for their records. Voila.
Not all vaccines are needed for school - but most are. Here is the cut and paste. If the booster is for a vax not on the list you do not even have to do the health unit thing.
"For children attending school in Ontario, a written immunization record or proof of immunization is required, by law, for diphtheria, tetanus, polio, measles, mumps and rubella unless there is a valid written exemption. Parents/guardians are required to provide this information to their local public health unit, and to update the information as necessary."