I would consider, not so much the distance, but the time taken. I can travel 20 miles in one direction and it would take about 20 mins. I actually travel 12 miles in the other direction and it takes about 30 mins, 40 in winter when fewer people cycle. I'd not do further than that to be honest, but I am old and lazy. If I was young and keen I might. You do need to consider out of school activities. Attending events in the evening does matter, as does taking part in clubs, etc., if you want to get ahead. Make sure you can manage that as well.