Dd1's homework was to put some verbs in the 'past tense'. Some of these have been marked as incorrect when she has used a past imperfect tense (was painting) rather than what I presume was the intended past perfect (painted). I have tried to explain to her that her answer is a correct past tense but that her answer would tend to be used if she then went on to talk about something else, so I was painting the door when I fell off the ladder. About half the words she used the perfect form and half the imperfect, it was just a list of verbs - paint, swim etc. Teacher's comment was that it was a good try. (She says that they haven't covered past imperfect. )