As far as first impressions go, fear feels near impossible to keep low - hint/reassure barely do anything and the only other way I can see is by forgiving rulebreak. It also seems basically impossible to raise discipline via exam actions while keeping fear low. Maybe it becomes easier with ultra high corruption/naturism, but thus far it looks like they just slow the rate of change rather than affect the 'direction' i.e. super corrupt girls grow/lose fear less but also gain/lose less discipline.
For example, here are the girls fear/discipline after a positive (encouraging) and negative (groping) event
You can see that the loss in discipline from encouragement is about twice the gain from groping but the fear change is a whopping 6 times. Similar effects occur for other events e.g. spanking.
Fear 100 isn't strictly speaking, purely negative, but IMO it is overall negative, so it is a pity that the current equations seem destined to force girls to either low discipline or high fear.
There are some portions of the code that use renpy.random.randint, which can cause an error if the range is invalid.