I am a hua xing medium school's headmaster.冠词a多余,后面表语已经是专有的,你见过说I am a Jim的吗,没有吧.另外medium是中号的,不对,应用middle.
you can hard working and you must like children. hard-working是一个合成词,词性为形容词.另外用can也不合适,用 you must work hard相对合适一点.
另外,第二段那一大堆can用的都不好,关键是我要求你需要怎么样,而不是你已经能怎么样.you need to/must be able to .更合适一点.
If you can do this thing.你前文说了那么多,最后怎么只是一个this thing.应该是these things吧,或者all of these.
you will have change to be a teacher.首先我不知道是不是你打错了,但这句话前应该是逗号,必须是逗号.另外这里我认为你想说的是chance而不是change,而且chance前必须要有冠词,
Wish you can success!把can去掉,wish you success就得了.
If you are interesting in.应该是interested...