Hiya dolly,
A lot of it depends on what qualifications you have, if you have a degree then you'll probably get the job assuming you have either experience of working with children or have been a parent helper.. other qualifications required are NVQ level 2 (minimum) in child care and education or NVQ level 2 Teaching Assistant. I don't think schools employ anyone who doesn't have any of these qualifications now.
You'll also be expected to complete an advanced CRB check.
It IS a very rewarding job but I will add that the pay is very poor especially if you get to a point where you're taking whole classes to cover for Planning & prep time or if there are any staff absences.
As for respect, that all depends on the head teacher and how you are with the children. (don't let them get the upper hand - the children that is, not the head!) Some T/A's have very little responsibility and have to do general dogs body jobs other T/A's have pretty much an equal amount of responsibility as the teaching staff (without the extra pay) I know of some schools who don't allow T/A's to sit in the staff room at break & lunch time with the Teaching staff..
Hope this helps, Good luck and good luck with the piano tuition too :)