Very little is forgotten during vacations--if anything, new things are integrated.
This reminds me on one tremendous waste of time. After summer vacation we used to spend a good two months reviewing lessons from the previous year. They seemed to assume we forgot everything, and that's when I honed my paper airplane skills, which eventually evolved into the development of model rockets propelled by fuel made at home. It was similar in composition to gunpowder. I got into a lot of trouble shooting these things across the classroom. My teacher actually confiscated around a pound of the stuff that I had in my desk. It was easily reproduced though, using ingredients available off the shelf in any drug store.
W