Cambridge English: Key, also known as the Key English Test (KET), is the lowest level General English exam in the Cambridge English range. It shows that you can communicate in basic English in everyday situations.
Cambridge English: Key for Schools (KETfS) is at the same level as Cambridge English: Key and leads to exactly the same internationally accepted certificate. The only difference is that the exam content is targeted at the interests and experiences of schoolchildren.
Level of qualification: Elementary = A2 on the Common European Framework.