The two sectors form a continuum, with VET at the lower end and Higher Education at the higher. VET courses are typically short, practical in nature and delivered by a TAFE college or Registered Training Organisation at a certificate to diploma level. Higher Education courses take three years or longer to complete, are academic in nature and are delivered by universities at degree level. There is significant overlap, however; a TAFE college may offer degrees and universities may offer certificates and diplomas. A number of private institutions and community education centres cover the full range of qualifications. There has been a strong push towards mutual recognition of qualifications, with VET or Higher Education courses recognised towards other courses (and for those under 21 towards an SSCE). A process of Recognition of Prior Learning (RPL) has been implemented to allow competencies gained through work and other experience to be assessed and recognised. For instance, a "Diploma of Agriculture" might be recognised as the equivalent of the first year of the "Bachelor of Agricultural Science" degree; a unit of "Letter Writing" in a "Certificate IV of Writing" might be recognised as a unit towards a "Bachelor of Business" degree; experience in aged care might be recognised towards a "Certificate in Community Services". All students doing nationally recognised training need to have a Unique Student Identifier (USI). Certificates I-IV are the basic qualifications and prepare candidates for both employment and further education and training. There is no firm duration for these qualifications. Entry for Certificate III and Certificate IV courses requires the completion of Year 10 or Year 11 education respectively. Certificates I-II provide basic vocational skills and knowledge, while Certificates III-IV replace the previous system of "trade certificates" and provide training in more advanced skills and knowledge. These courses are usually delivered by TAFE colleges, community education centres and registered private training providers. Courses at Diploma, Advanced Diploma and Associate degree level take between one and three years to complete, and are generally considered to be equivalent to one to two years of study at degree level. "Diploma" and "Advanced Diploma" are titles given more practical courses, while "Associate degree" is given to more academic courses. Entry into Diploma and Advance Diploma courses requires the completion of Year 12 education. These courses are usually delivered by universities, TAFE colleges, community education centres and private RTO's (Registered Training Organisations). The Bachelor degree is the standard university qualification and is recognised worldwide.