What is the test for variation in child support?

Sopinka J. went on to say, at p. 691: Having found that the conditions for variation exist, the trial judge should proceed to determine what variation should be made. The trial judge must re-assess the needs of the children in light of the change. The needs of children are not assessed in a vacuum but are affected by the standard set by the means of the parents. When the means of parents are limited, the children's needs may be satisfied by the bare necessities. In these circumstances the children are required to do without some things which would be available to them if the means of the parents were greater. The reasonable expectation of the children for future support upon marriage break-up is conditioned by the standard of living of the parents at the time. This expectation is not frozen as of the date of marriage break-up. If there is a significant change in the circumstances of one of the parents subsequent to the support provisions, the reasonable expectations of the children will be affected. In this regard I agree with the statement of Kelly J.A. in Paras v. Paras, [citation omitted], when he states: Since ordinarily no fault can be alleged against the children which would disentitle them to support, the objective of maintenance should be, as far as possible, to continue the availability to the children of the same standard of living as that which they would have enjoyed had the family break-up not occurred.