Because you are a volunteer and not a paid educator who works at least 900 hours a year, you cannot use the above-the-line deduction of up to $250 from gross income (allowed even if you don’t itemize, assuming this break is extended for 2015). However, if you donate the supplies to the school and do not restrict their use, you can take a charitable contribution deduction for your out-of-pocket costs. To do this, you must (1) itemize your deductions, and (2) have obtained the required substantiation for these costs (including an acknowledgment from the school if the cost is $250 or more).
Rule for determining MACRS depreciation in the year property is placed in service. Either a half-year convention or mid-quarter convention applies.