Neither of those is quite right (and none of the answers you've been given so far is correct).
It isn't clear what you are trying to say, but the main problem seems to be the preposition 'in'. Do you mean 'most of the time', meaning 'usually'? If you do, you can say 'the majority of the time', without 'in'. For example:
"The majority of the time, the children behave well. They rarely fight'.