A: This is appalling. You are being exploited as a part-timer and a newly qualified teacher. Your headteacher is breaking the law and you need to raise the concern. Here's the key reference for heads from the Department for Education and Skills' guidance on induction, The Induction Support Programme for Newly Qualified Teachers (Reference: DfES04582003) at www.teachernet.
gov.ukprofessionaldevelopmentnqtinductionguidancerolesrespheadteacher: "NQTs must have a timetable of no more than 90 per cent of the timetable of other mainscale teachers in the school without responsibility points to allow their induction to take place. Under the school teachers' pay and conditions document 2004 (paragraphs 57.8.4 and 57.8.5), you are placed under a duty to ensure NQTs' teaching time does not exceed 90 per cent of the average."