Parents Locking Down Almost 18 year-old??

I need your opinion, my parents have decided to make me quit my job of two months (I work as a nanny, I get to study at the residence and am doing well with my grades) on the premise that I don't study enough and that it strains my time working around the house and also that I'm getting paid chump change ($20-$40 a day, I know it isn't much but there's no one hiring and my parents do not have my IDs)

I love my job and don't want to let it go.

(They want me to work as a maid for a perfectly healthy family member once a week for $30 and MAYBE get paid extra from doing a list of chores immaculately)

But why are they all of a sudden taking away dates and my job like it's nothing to me?