Happiness does not come about only due to external circumstances; it mainly derives from inner attitudes. – Dalai Lama
We always let the kids study throughout the summer, it could be as simple as they need to regularly read a book (any book or even comic would do as long as they read), we always get some sort of summer reading bingo from the school which we use and they then also get to show the teacher. We always make sure that they also do some math and something which would benefit them personally.
Both me and my husband has read Outliers by Malcolm Gladwell, which discuss that success (in whatever area that is important to you, from playing guitar to run a business) is to build up 10 000 hours of practice, he also talks about the importance of keeping the flow of learning going throughout the summer break. They did a study and discovered that the students which had studied throughout the summer overall had a much better result than those who did not, even though those who did not study learned more and faster after the break. We are now, of course, trying to instill this in our children. So today I have started to look and plan for this summers courses with mum. There will be math, reading and potentially history for the older son.