If you are in the UK studying on a Tier 4 visa, your work conditions will be printed on your biometric residents permit (BRP). Always check the stamp in your passport or your BRP to see whether you are allowed to work and for how many hours a week.
If you are allowed to work, your maximum working hours in term time are:
20 hours a week if you are studying at degree level or above at a higher education institution (HEI)
20 hours a week if you are on a study abroad programme at an "overseas higher education institution" in the UK
10 hours a week if you are studying a course that is below degree level at an HEI
10 hours a week if you have immigration permission as a Tier 4 (Child) Student and you are at least 16 years old.
Students on a short term student visa are not allowed to work. This included both paid and unpaid work.
If you want to volunteer, it is really important to check whether the work you are doing could be classed as unpaid work.
ASK can help if you have any questions.