If you are from a country in the EU you will not need a visa.
If you are from a country outside of the EU then it is very likely that you will require a visa.
Adult students will need either a “student visitor visa” or a “general student visa” depending on the course length.
Students up to 17 years of age will usually only require a “child visitor visa”.
The best place for information about visa application is the UK Border Agency (UKBA) website. Please click here to visit the UKBA website.