If school meets for 10 months out of the year then what fraction are students off?

There are 12 months in a year. If school is in session for 10 months, then students are off for 12 - 10 = 2 months.

Therefore, the fraction of the year students are off is $\boxed{\frac{2}{12}}$, which simplifies to $\frac{1}{6}$.