What do you say if your younger brother or sister is lazy about studying?

I will not say anything
but what i am going to do is to report this behavior to our parents. if my younger brother or sister does not listen then i think i will not help him/her with his/her homework (as simple as that) normally when our parents talk my younger brother or sister will listen

"don't be lazy! if you're lazy to study, you will not get great value in your school exam, and your future will be bad. so you have to be diligent to make your future bright."