Despite the downward trajectory of bonds over the last year, in general the bonds will not be as volatile as stocks. At age 17 the moderate portfolio is all in bonds and short-term reserves, and the aggressive portfolio is 25% stocks. If you've split 50/50 you're only 13% in stocks and even if they got cut in half you'd only be down 6-7% and your bond funds would almost surely go up. I think the risk of a 30% haircut between now and college graduation is extremely low.