There are different levels of teaching assistant and none of the levels are pointless! An NVQ level 4 does not qualify you as an HLTA, you would still need to do the qualification or you could be deemed to be qualified by your headteacher (this is not portable). I would suggest that a level 2 would allow you to apply for a teaching assistant post. In my LA there is a lower level Classroom Assistant which has no qualification requirements. Once in post your school would probably put you through the next level NVQ at their expense. It would be a good idea to contact the HR departement in your LA and ask which qualification they prefer.