As a high school teacher I agree 100%. Learning by accident is essentially what happens when students engage with a presentation or activity that they see as being fun.
Not everyone is a born entertainer; cheesy jokes badly delivered will turn off even the most attentive of learners, so there is perhaps some distinction between engaging and entertaining. This is essentially about ‘knowing your audience’ and using tools that will engage them. With high school children this is age-specific and things that work include music, sarcasm and sweeties, although not all at once!