This is just one lawyer, who stands to make a lot of money. So maybe things were not as bad as he says?
Australia is currently having a Royal Commission into Institutional Sexual Abuse. Things like schools, orphanages, youth clubs, etc. That Royal Commission has exposed the fact that sexual abuse of children was disturbingly common in almost every major institution that gave people potential access to children. It was only a small proportion of the adults involved - but even one molester in a boarding school or other closed environment could potentially access many victims.
I doubt this was only true of Australia. It's just we finally reached the stage of looking into it properly after many years of denials.
As somebody who attended such a school, and who teaches in one now, it's horrifying and appalling. But all to easy to believe.
In most cases, it was quite a long time ago - while there were later incidents, most of what is coming out now happened in the 1970s at the latest. After that, most institutions did get better at stopping these things from happening. But when I was at school in the late 1960s and early 1970s - when I look back, while I wouldn't say I was molested - not quite - there are certainly a couple of teachers who I believe probably did it to other boys. And my old school has come out of the inquiries reasonably unscathed - some of the ones named in this report seem to have had very big problems.