What do your GCMS notes say? I am not sure I would apply for a fourth time if you already have three refusals without the help of an immediate lawyer. Please make sure you are working with an actual lawyer and not a consultant. It's possible an approval will not be feasible so you will need to consider what you do in the event a visa cannot be obtained. Unfortunately it was a big error to indicate your child as non accompanying in your WP application. Good luck and hope something works out.
Below the GCMS notes and refusal letter indicated.
First time it was rejected because my consultant missed to submit the Father's concent letter. Second time for the reason that in principle, my WP submission application the consultant has tick marked I am not accompanying any family members. Third time as below:
I am not satisfied that you will leave Canada at the end of your stay as required by
paragraph R216(1)(b) of the IRPR (
https://laws-lois.justice.gc.ca/eng/regulations/sor-2002-227/
section-216.html). I am refusing your application because you have not established that you will
leave Canada, based on the following factors:
• Your proposed length of stay in Canada is inconsistent with a temporary stay given the
details you have provided in your application.
• The purpose of your visit to Canada is not consistent with a temporary stay given the
details you have provided in your application
And below what is written in the GCMS notes.
I have reviewed the application. I have considered the following factors in my decision. The applicant's proposed length of stay in Canada is inconsistent with a temporary stay given the details provided in the application. Given the availability of good primary school education programs in the applicant’s home country as well as the region, at a fraction of the cost in Canada, not satisfied that the proposed study is reasonable. Weighing the factors in this application, I am not satisfied that the applicant will depart Canada at the end of the period authorized for their stay. For the reasons above, I have refused this application."
This appears to be a visa refusal letter, stating concerns about the temporary nature of the stay, availability of education in the home country, and doubts about the applicant's departure from Canada after their authorized stay