Its always easier to see mistakes when you find something unexpected, you read things other people have done without prior knowledge. Re-reading your own material is more difficult to spot mistakes, because you know what it says already.
Teachers were a sore point for me too. As my name is Alasdair, I don't necessarily expect people to know how to spell it instantly, but as a teacher should be setting examples it put me off when I brought home a school report with 10 different spellings of my name, none was correct