There's a range of routes into teaching for undergraduates:

School Based Initial Teacher Training (SCITT)

In order to enter a study programme leading to an undergraduate degree, you will usually need to have at least two A-levels or equivalent. You can combine your undergraduate degree with gaining Qualified Teacher Status by studying for a BA(QTS), a BSc(QTS) or a BEd(QTS). This will usually involve full-time study for four years, although it may be possible to find a part-time course. Alternatively, you can spend three years completing an undergraduate degree in a relevant subject and then pursue graduate routes into teaching.

Applications  are handled by UCAS. Please visit http://www.ucas.com/how-it-all-works/teacher-training/postgraduate-routes-teaching/training-in-schools for more information on applications.