男孩 - nánhái - boy
上 - shàng - to attend (class, school or university)
小学 - xiǎoxué - elementary school / primary school
年级 - niánjí - grade / year (in school, university etc.)
孩子 - háizi - child
弟弟 - dìdi - younger brother
觉得 - juéde - to think / to feel
上学 - shàngxué - to go to school / to attend school
重要 - zhòngyào - important / significant / major
家里 - jiālǐ - home / at home / in the home
穷 - qióng - poor
晚 - wǎn - late
数学 - shùxué - mathematics
大学 - dàxué - university / college

Number 1 + Number 2 - Expressing approximation between two sequential numbers with "Number 1 + Number 2"
他的同学都是七八岁的孩子。

Phrase + 的 + Noun - Expressed to link a noun to a preceding phrase with "Phrase + de + Noun"
他的同学都是七八岁的孩子。

Subject + 跟 / 和 + sb / sth + 一起 + Verb - Expressing a subject is doing an action "with" sb or sth "together" with "Subject + gēn / hé + Person + yīqǐ + Verb"
他有一个弟弟，今年九岁，和他一起上一年级。

因为 + Reason，Result - Expressing "because of..." to introduce the reason that causes the result with "yīnwèi + Reason，Result"
他们的爸爸觉得上学不重要，也因为家里太穷了，没有钱让他们去上学。

(在)...里 - Expressing "in / inside…" with "(zài)...lǐ"
他们的爸爸觉得上学不重要，也因为家里太穷了，没有钱让他们去上学。

Subject + 让 + Sb / Sth + Verb / Verb Phrase - Expressing "to make or let sb / sth to do sth" with "Subject + ràng + sb / sth + Verb / Verb Phrase" (causative verb)
他们的爸爸觉得上学不重要，也因为家里太穷了，没有钱让他们去上学。

Statement， 但是… - Expressing "but / however…" with "Statement，dànshì…" (a bit more formal than 可是)
吴元吉的老师说他上学很晚，但是他的数学很好。

Subject + 想 + Verb + Object - Expressing "would like to" with "Subject + xiǎng + Verb + Object"
他也很想上大学。

云南 - Yúnnán - Yunnan (Province)