Need to persaude my mum to let me out late at night

i'd like to spend the day in the city with my friends, and come home earliest around 8:00pm. The only problem is my mum doesnt want me to go into the city for 2 reasons. 1. she wants me to go to church at 6pm that night 2. she doesnt like me in the city late on a saturday night (drinkers, parties, fights etc.). Any help persuading her?