For K-12, you enter tuition in the 1099-Q section, not in the "Educational Expenses and Scholarships section". After entering the 1099-Q, a screen will ask what level of school did the student attend. You must answer high school or elementary (K-12 isn't a choice) to get the screen to enter expenses.
But, you probably don't need to enter anything. The 1099-Q is only an informational document, if you know it's not taxable, because you tuition was equal to or more than (up tp $10K) the distribution, you do not need to enter the 1099-Q.
On form 1099-Q, instructions to the recipient reads: "Nontaxable distributions from CESAs and QTPs are not required to be reported on your income tax return. You must determine the taxability of any distribution."
