One of the biggest challenges facing higher education, according to University of Tennessee president Dr. Joe DiPietro, is the number of students who leave high school who are not prepared for college."Of all the students who enter community college in Tennessee, 70 percent need remedial work," said DiPietro. "And if they need remedial work, there's only a 1-in-5 chance they will complete their courses on time."DiPietro made those comments Thursday while addressing members of the Rotary Club of McMinnville.Another major obstable to attaining some form of post-secondary education is the soaring cost of tuition. DiPietro said students paid about 25 percent of the cost of their college education in 2001 with the state paying the remaining 75 percent.Now he says those numbers are flipped with the students paying about 60 percent of the costs and the state paying 40 percent."If you look at tuition increases we've had in recent years of 6, 8, 12 percent, that is a model that is unsustainable," said DiPietro.