Summer schools: plus or waste of time?

I've attended a Finance-oriented summer school at the LSE and can tell from personal experience that it was definitely worth my while. Although it certainly cost me a fair dime, the network and experiences I built up over the span of a mere three-weeks have proven to be incredibly useful.

For example, I've recently applied to my target schools for a Master's and was often able to reach out to summer school classmates who had been through the exact same process a year prior. They could give me the ins-and-outs of each programme at each school and whether or not it would suit my preference.

On the more social aspect, it was absolutely amazing. Not only did I get to explore London's amazing nightlife almost every other day, I also built friendships and connections with people from e.g. the US, Spain, Portugal, Germany, the Netherlands, Italy, Dubai, etc. Be advised though, in my course the reading was quite heavy, but luckily I managed to combine the social and learning experiences.