The Pell Grant program, the bedrock of our country's investment in education, already makes college tuition free - or mostly free - for more than eight million low-income students. With a maximum award of more than $5,000, Pell Grants cover tuition at most community colleges and, when combined with need- or merit-based institutional aid, can make many public or private colleges affordable, too. It would be far better policy to double our investment in Pell Grants, broadening the number of those who can benefit from them, than to make tuition free for all, including those who have the means to pay.