In Sanya, Hainan, there's a small population of Utsuls, 回辉人, descendants of Cham people who fled the Champa kingdom in today's Vietnam.
They're also known as Hainan Hui, being misclassified as Hui people.
They are predominantly Muslims.

Although Chinese law bans "religious activities" in schools, there is no national regulation that bans wearing religious clothing or symbols in schools. Until recently hijabs were only banned in Xinjiang schools, especially in the south (Tarim basin).

Since last year there has been news of hijabs being banned in Utsul schools in Sanya. OP is about the most recent incident. Female students wearing a hijab were not allowed into the school and were studying outside.
this isn't surprising as the "sinicization"

of Islam is being implemented.
what gives me chills is the online discussion abt this on weibo & douban
the unreserved support for the ban, the praise of XJ "model", and the overt Islamophobia & xenophobia ("they are descendants of refugees, this is not their country")

ironically the douban thread full of these messages has been censored.

在贴子被删之前我截屏了几条觉得特别讽刺的，学校取消佛学课程还觉得特别理所当然的，反驳别人宗教自由的观点却连“宗教”两个字都怕是敏感词发不出的。心太累不想翻了。