How to Approach This..?

I'm 16, still in high school (going to be a senior) and have 2 new baby brother, well they are almost 1, anyway last school year after they were born it was quite stressful to watch them, do chores and continue to do good in school...to not fall behind.

My mom has told me that school comes first, but I have a feeling I'll be watching the boys all school year again and i don't think i can handle the stress of it all..(Im taking college courses and AP classes)

How should i approach my parents about not watching them all the time? (my dad is more on my side about not watching them as often). Im completely willing to help out its just.. this is the year where i should figure out what i do with my life..i want to minimize stress😥