As a master's student, I've recently attended my first summer school. I waited for it eagerly since there would be learning about my research topic, interacting with other students and travelling. But it turned out to me that it combines pretty bad.
Every day consisted of multiple lectures each of 90 minutes. It's hard to keep attention for a new, quite technical material for such a long time. Sometimes you realize that you cannot ask the lecturer for an explanation since you even cannot formulate the question. Also, I've made sure (as I've long suspected) that I'm a book kind of student - I study much better with lecture notes or video records, not with live talks. As a result, I think I got (even incompletely) less than 25% of talks.
The travel part was also not so good since the school was being held in regular working hours of museums and all. I had walked a lot at evenings and enjoyed it, but compared to my regular travelling experience it wasn't enough.
The social part was good though, I think I was pretty good at networking.
Concluding, it seems that I've spent my time very inefficiently. I'm sure that I'm not alone in such experience. But AFAIK schools, conferences and workshops are all conducted in this way. And I will be expected to attend them.
How can I make myself more productive in such events? Currently the only way I see is to attend only lectures I'm sure to understand and just skip others, trying to read papers and slides by myself or just hanging around the city.