They were victims not because of their age, but because they were subjected to inappropriate and exploitative sexual behavior in an institutional setting by an authority figure. Frankly, though, an older man with teens—that’s an age difference that might inform a reasonable analysis of the power relationship.
“Abuse of trust” is a relevant term in other jurisdictions that have had to legislate directly against instructor-student sex (such as the UK) due to lower ages of consent.
One thing I’d like to stress is that the womens’ agency and consent should not be enough to get him off the hook, because his responsibilities are not to them exclusively.
There are many things adults cannot consent to.