Why were children not allowed on busy train?

I WAS amazed to see on TV on Saturday October 1 that six or seven young people were not allowed to join a mid-morning train from St Austell to Truro, on the presumed grounds that the train was overcrowded. It was indeed the case that some passengers were seen to be standing, but there was surely enough room for the few children wishing to join the train. In any case why not put on an extra coach to satisfy the demand? Peter Castle 2 Holly Bank Church Hill Whitchurch