<p>How much does he like math? My “mathy” D loved the on-line Thinkwell program, which has lectures, problems and a book. If he would enjoy that, it is a great program for the summer. Khan and AoPS are also reasonable and excellent.</p>
<p>If he would not enjoy math for it’s own sake, I would suggest not pushing it at this time - wait and see how geometry goes.</p>