我是在初一的时候开始学法语的。

Wǒ shì zài chūyī de shíhou kāishǐ xué Fǎyǔ de.

I started learning French when I was in seventh grade.

我妹妹今年上初一了。

Wǒ mèimei jīnnián shàng chū yī le.

My younger sister started seventh grade (the first year of middle school) this year.