It is common to need:
five GCSEs at grades 9 to 4 (A* to C), or equivalent, including science and English
A level
It is common to need:
A levels, or equivalent, including a relevant subject like biology or physical education (PE).
Degree
It is common to need:
a bachelor's degree (BA or BSc) with qualified teacher status (QTS) in PE
Some employers may accept a degree in physical education or sports science without QTS, but graduates will need to train on the job to gain QTS.