Great care has been taken in the design of Story mode to make the mathematical difficulty increase at just the right rate for almost all pupils.
We should all anticipate a certain amount of "struggle" to pass some levels - that's the nature of learning and improving, of course - so it's appropriate that pupils take between 1 and 5 attempts to pass a level, on average.
If you receive feedback that a pupil is having significant difficulty, take a look at what the data is telling you... go to Stats > Story Record and check the pupil's average attempts to pass each level. Is their average-attempts-to-pass looking high? And have they had many attempts to pass current level?
There will be individual pupils, however, for whom the time constraints required to pass the Story levels are demonstrably too tough for them.
In those one or two cases, having considered other options such as gentle encouragement, offline help from a grown-up, etc., the most sensible way forward is to relax the time constraints somewhat for them.
Two and Three Times Easier
Teachers can give certain pupils two or three times longer to answer each question by going to the Story Controls page, and moving the pupils' name tags into a group, then setting that group on "2× longer" or "3× longer".
Alternatively, if your pupils have more experience and are finding NumBots too easy, find out how you can allow them to skip the early Story levels, in order to reach a more relevant maths topic, here: