Born and raised in Africa, I had always taken my African origin as a burden. My self-dislike was further fueled when my family had to relocate to Norway, where I attended a high school. Compared to all the white girls around me, with their golden hair and delicate lips, I, a black girl, had curly hair and full, red lips. My nose often had a thin sheet of sweat on it, whatever the weather was. I just wanted to bury myself in my shell crying “I’m so different!”

What also contributed to my self-dislike was my occasional stuttering (口吃), which had weakened my self-confidence. It always stood between me and any fine opportunity. I’d taken it as an excuse to avoid any public speaking sessions, and unknowingly let it rule over me.

上面的内容摘自2022年高考英语天津卷（第二次）的阅读理解B。

问题：上面的 attend a high school 为什么要加冠词？不是应该说 attend high school 吗？又如：go to school, come to school 等。