I am not sure why you are signed off - if due to stress/depression/mental illness of some description, it may be worthwhile discussing staggered return - and even better if you can get this matter of end of year reports addressed by OH before your return... The problem/issue will be linked to you being the class teacher and as such ultimately responsible for the reports if you are fit to work - so if you return/are planned to return any time much before the reports are due out you could be expected to write them... If you have been absent for quite some time, this could be even more complex an issue and you are right to try to plan for your return... Sadly many HTs will see it quite cut and dry - you are their teacher, you write the reports! I even know one teachers who had only taught the class for the first six weeks of the year and then returned two weeks before the summer holidays and was told to write the reports!