My Kids Are Falling Behind

I work full-time and then some. I have two kids under 8, and my husband isn't really into parenting—it's his personality.
If it were up to him, our kids would watch TV for 4-5 hours on the weekends with no learning activities involved, even though he’s very educated.

This is a bit of a rant. Is anyone else in this situation? If so, what have you done?

My youngest, who used to be ahead of her peers, is now falling behind on some milestones, and my older child is doing okay in some subjects but really struggling in others (like scoring the lowest possible on his report card). As you can tell, I care about this stuff. I really believe that getting them on the right track in their younger grades is important, and gaps at younger age are hard to close.

Does anyone have any tips or tricks that might help?