A majority of Americans believe college is an investment in their child's future, but it's one they're not adequately preparing for.

Only 48 percent of parents are saving for their child's education, down from 51 percent last year, according to Sallie Mae's new "How America Saves for College 2015" report, which surveyed 1,988 parents with children younger than age 18. Families' average college savings balance has decreased, too, dropping 25 percent from $13,408 in 2014 to $10,040 in 2015, the lowest level in three years.