This is an Education Service Advisory Committee list, so it's probably about 20 years old; I can't believe much has changed (though presumably 'covering for absent colleagues' is no longer such an issue).
Students:
inappropriate class sizes
actual violence, or threats of violence against teachers
violence among pupils
disruptive pupils
uncertainty about the limits and scope of discipline
poorly motivated students
teaching low ability students in mixed ability classes
Colleagues:
lack of communication
personality conflicts
unfair distribution of workload
Management:
badly managed change
lack of involvement in decision-making
differing and changing management styles
prolonged conflict
bullying
lack of support from managers
too many after-school meetings
workload covering for absent colleagues
workload teaching unfamiliar subjects
lack of career development
under-promotion
over-promotion
failure to realise that different teachers react to change differently
too much working at home
poor working environment and working conditions
Society:
lack of status
lack of understanding of a teacher's role and limits
changing expectations
anxious parents
aggressive parents
The Teachers Themselves:
unrealised expectations
sense of injustice or bitterness
inadequate training or experience