since you have not declaraed you had a dependent child, nor at time of landing. Normally CIC gives you at least three chances to declare: 1) at submission your application; 2) during processing and 3) at landing. If you have declared (which means you have signed in your Confirmation of PR at time of lading), you will lose your right to sponsor him or her, forever.
However the child may be eligible to study up to grade 12, even he is not a PR of Canada, as per some government policy (if you know where to obtain them). In another words, your child can study here without paying higher tuition fees like internation visa student. AND HE HAS TO MAINTAIN HIS LEGAL STATUS IN CANADA, WHICH MEANS TO GET VISITOR RECORD (EXTENSION ) FROM CIC.
However the child may be eligible to study up to grade 12, even he is not a PR of Canada, as per some government policy (if you know where to obtain them). In another words, your child can study here without paying higher tuition fees like internation visa student. AND HE HAS TO MAINTAIN HIS LEGAL STATUS IN CANADA, WHICH MEANS TO GET VISITOR RECORD (EXTENSION ) FROM CIC.