Potty training poos

How long did it take for your little ones to poo on the potty. We started potty training end of August and she is still starting poos in her knickers. Sometimes she will then finish in the potty after sitting for an hour. We kept her home this week as she was having too many accidents at nursery. Now I’m thinking she will do the same next week and have lots of accidents. Does it usually take this long for them to learn to poo on the potty.