Last time I looked at this (late last century), results scaled inversely to class size (so one might consider oxbridge 1:2 recitations as almost optimal), but for polities that don't prioritise educating their children, somewhere around 1:12 seemed like the knee of the curve.

> Amid a teacher shortage, labor challenges persist in hiring tutors.

A teacher shortage sounds like insufficient teaching pay to clear the market, which suggests that attempting to hire an even "cheaper teacher" (ie, a tutor) would be difficult to do effectively.