CHICAGOWith winter's onset driving the demand for surface coal to record-high levels, the mineral's cost is now beyond the reach of low- and middle-income Americans who wish to punish their naughty children. 'Coal in one's stocking is meant to serve as an admonishment or warning, not as a dependable grade-B investment,' said William Menchell, a commodities adviser for T. Rowe Price. 'In today's market, children should only have their stockings stuffed with lumps of coal if they have been studious and obedient, and show an interest in long-term investments in the energy sector.' For more affordable punitive options, analysts point to the relatively stagnant switch market, which could soon go the way of coal if demand increases for combustible wooden sticks. 