1 Recognition of achievement. In further and higher education, a student may accumulate credit, for example in the form of a number of modules successfully completed, each of which carry a number of credit ‘points’. The accumulated credits may be used to gain a recognized qualification, such as a certificate, diploma, or degree. This is sometimes colloquially termed as ‘cashing in credits’. A candidate may also transfer credits from one institution to another, adding those gained in one institution to those gained in the next. This is known as ‘credit transfer’. Credit accumulation and transfer (CAT) is the term used for both parts of this process.
2 A grade awarded for successful achievement in an examination or other assessment, indicating attainment beyond the minimum level of a pass. It is the highest level of Standard Grade qualification in the exam taken by students aged 15 or 16 in Scotland. The three levels are Credit, General, and Foundation. Students will usually sit two levels at the same time; hence Credit students will also sit General papers and those taking General level will sit Foundation papers.
http://www.ltscotland.org.uk/nq/nqframework The Teaching and Learning Scotland site gives a clear overview of the levels awarded at Standard Grade.