University students 'cannot spell' - Telegraph: "Many undergraduates misspell basic words such as 'their', 'speech' or even 'Wednesday' in essays, it is claimed. First year students are the worst offenders, despite already spending at least 13 years in the education system. Standards have deteriorated to such an extent that one leading academic has been forced to ignore common errors altogether. Dr Ken Smith, a senior lecturer in criminology at Bucks New University, said 'atrocious' spelling was rife among new undergraduates, with many failing to apply basic rules, such as 'i before e, except after c'. The words 'weird', 'seize', 'leisure' and 'neighbor' are regularly misspelled by students, he said."
These are Brits, but the same holds true here in the US. It even happens in papers written using word processors that have instant spell checkers.