It's hard,parents do not like to see their kids get a "missed" assignment or "fail", but we found out, they need to deal with the consequences (sp?) otherwise we are enabling them, my son's grade school teachers use to preach that, and besides it's his homework not yours.
My son, for some reason waits nearly to last minute, and hasn't gotten any help from us, since 8th grade, he's in his 2nd yr of college,with scholarship,etc.
He also did excellent in HS. So funny, till this day, I'll say, "do you have homework?", and of course it's near last minute.
Some people work best the last minute, while many of us need to plan. My complaint to him was, if he spent more time he'd even get better marks . . . well he still gets great grades. I guess that is his nature, but had we always weakened, I do not think he'd do this well, cause he wouldn't have learned what "responsible" means.
I use to love when the night before (late too) we would hear, "oh, I forgot I need certain paper,pen, or whatever he would need for a project due the next morning.
Driving all over to find a 24 hr grocery store or quick mart store. Yep, 8th grade was the final straw.
It's great when they are driving, they learn they have to get up and get what they need.
"Be gentle, but be firm", I use to say, when training our dogs, it helps with kids too.
Lots of luck