Schweser says that for a given duration, the greater the convexity, the lower the interest rate risk. The wikipedia page for convexity (top line) says the higher the convexity, the more senstive the bond price is to changes in interest rates. Which is correct?

It depends on which way interest rates change. If YTM decreases, higher convexity gives a greater price increase, but if YTM increases, higher convexity gives a smaller price decrease. In either case, higher convexity is better than lower convexity: more upside, less downside.

Easy way to remember this - draw it out. Takes a couple seconds and is an easy way to figure it out on the fly.