小学(xiǎo xué) - primary school in Mandarin

小学 (xiǎoxué) is primary school. 小 (xiǎo) means "small" and 学 (xué) here means "school", so it is literally a "small school", the stage before 中学 (zhōngxué), "secondary school".

Chinese primary school normally runs from age six to eleven or twelve, six years in total, and a pupil there is a 小学生 (xiǎoxuéshēng), "primary school student". 上小学 (shàng xiǎoxué), "to attend primary school" or "to start primary school", is the standard phrase for both being enrolled and beginning.

一所小学 (yì suǒ xiǎoxué) is "one primary school", using 所 (suǒ), the measure word reserved for institutions like schools and hospitals rather than the general-purpose 个 (gè).