you mean you want suggestions on dissertation topics ? well, i do not know if these topics will be interesting or redundant but they will make things easy for you if you want a get-away topic
1. error analysis
2. Contrastive Analysis
3. teacher feedback
4. skills' integration
5. the communicative approach (for instance search why teachers are not using it in their teaching )
6. Assessment procedures (assessment Validity : you can refer to the fact that the learners are not always assessed the way they have been learning )
7. the effect of anxiety on the learners (caused by the teachers of course)
8. see for instance the problems of writing in English (paragraph, essay )
9. try for instance to check the degree of the learning materials suitability to the learners of secondary school
if you want some explanation i can help you enjoy and good luck