What is the current state of the law on retroactively retroactively applying to schools?

In the case of Acme Village School District v. Steele-Smith, 1932 CanLII 40 (SCC), [1933] S.C.R. 47, recognition was given to the two conflicting presumptions, "that statutes are not to be construed as having retrospective operation unless such a construction appears very clearly in the terms of the Act, or arises by necessary or distinct implication," and "should not be given a construction that would impair existing rights, unless that effect cannot be avoided without doing violence to the language of the enactment."