Router With Advanced Parental Controls?

I am looking for a home router that has more sophisticated parental controls that what I have been able to find. My kids need internet access for school. The problem is the amount of time they spend on Facebook or YouTube rather than researching their school work. At the same time I do not want to block those sites completely, just limit their use. Does anyone know of a router or software program that will allow me to give kids a daily or weekly “time budget” on sites like Facebook yet allow then unrestricted time on other sites for schoolwork? Thanks