What to do about F's...

One of my biggest problems this year is the number of students who have an F; I feel like my expectations are too low as it is, so I don't want to lower them even further, but at one point 45 out of my 75 students were failing! So here's what I've been doing:

Each Wednesday I give each of my failing students what we call "slips"; they are slips of paper that have the student's name on it along with their current grade and their "goal" (which is 5% above their grade for my gen. ed. students, and 3% above for my students with an IEP). I also list five assignments on the slip that the student currently has an F on and that will help their grade the most if they get a passing grade. I reiterate weekly that they don't have to finish all the assignments to pass, but they are just a list of ideas of some things they can do to meet their goal.

My students with slips have until Tuesday to meet their goal (I picked Wednesday/Tuesday so they have a weekend in there to work on some stuff). If they meet their goal there are no consequences or rewards, but if they DON'T meet their goal they have to take home a progress report to get signed by their parents and bring back the next day. If they don't bring the progress report back signed then they have to call their parents in class and explain that they are failing and didn't get a progress report signed, and that they will need it signed that night.

At first everyone had a goal of 70% (the lowest passing grade), but for the students who had a 10% or 40% it just wasn't realistic of me to expect them  to turn it around so much in one week. I have talked with our EC (special education) teacher, and she said some of our mutual students love getting those slips, because it helps them know exactly what they need to do, but I still have about 20 students each week who don't meet their goal and never care to try. If anyone has any suggestions for changes or ideas of what I can do about my F issue please share!