I am confused. Are you employed full-time as a teacher by your school (covering PPA)? If so, then I can't see how you can apply. The Head employs x number of teachers on the same contract, and then deploys them as he/she sees fit. You are already contracted to the school as a teacher, and the school needs another one. The Head has, presumably, worked out at least a draft staffing plan for September, which includes yourself (PPA again?) and has identified the best place to put a new starter as Reception. In order to put you in Reception, then the HT would have to (a) cancel the whole recruitment process as the candidates presumably thought they were applying for a post which was initially in EYFS, and then (b) readvertise a post which is initially PPA cover. If the HT wanted to deploy you in Reception, then he/she would have done so. The only opportunity for you to apply would be if you wish to change your contract with the school: ie your contract is part-time, or the advertised post has responsibility attached to it (ie it would be a promotion for you).