这是过去分词短语做后置定罢了.可以这样的理解,
she started a school magazine which is called New Standard when she was a pupil here.
这就相当一个定语从句,只不过是简化了一些.
再者,英语多后置定语,而汉语则恰恰相反,大多是前置定语.这点有心理有个数.
好了,愿对你有所帮助.
gooooooooooooooooooood luck