“Use it or lose it” and “Practice makes perfect” are two common expressions that you often hear, and for good reason because they are absolutely true. Think of your language ability like a muscle; the more you use it, the better it becomes. You may be getting ready to take a vacation from school, but don't take a vacation from your English-learning, too! Here are some tips for ‘exercising’ your English skills while on vacation, or anytime:
  Speak speak speak. Don’t be afraid to make mistakes! Make friends with others learning to speak English and with native-English speakers. Be confident and speak to as many people as possible as often as you possibly can. Doing so will boost your grammar, vocabulary, listening, pronunciation, and confidence.
Make use of the Internet.The internet is full of resources to help you learn: BBC Learning English; Learn English; Breaking News English. If you cannot find anyone to speak to face-to-face in English, the next best thing is to interact with others online via social networks–Twitter, Facebook, and Google+, for example. There are also several social networks designed specifically for foreign language learners such as Livemocha, Italki.com, and My Happy Planet. These sites offer the chance to interact with native language speakers from around the world, offering many features including podcast lessons and free text and video chatting.
  Immerse yourself in English. Find ways to make English part of your everyday life. The number of expats living in Korea increases every year, and with it, a multitude of English-speaking services. You, too, can take advantage of such services. Whatever you enjoy doing, it is possible to do in English. Take a cooking or a yoga class in English. Join a book or sports club. People learn more when they are having fun. Find something you love to do, and do it regularly -- in English. 
   Expose yourself to language. Expose yourself as much as you can, as often as you can, to as many sources as you can. Watch English television shows, movies, and YouTube videos; listen to English music and radio (my personal favorite is TBS eFM); read English newspapers, magazines, and books.
So remember, a vacation from school does not mean a vacation from English! If you sincerely want to improve, you should make English a big part of your everyday life, and your vacation is the perfect opportunity to do just that!