英语问题....翻译的..帮忙检查了！

第一句OK
第二句，他看上去不诚实 用He doesn't look like an honest boy.更自然、
第三句 他不在 这一层意思 用英语的名词his absence来表示会 更地道The head teacher didn't realize his absence.
第四句 应该是个运动员 既然是“应该”么那就把 may 改成 should吧！另外还有一个语法错误，wear请用单数， the man who wears a blue T—shirt should be an athlete..

第一句是对的，其他有些语法错误。
It seem(s) that he is not (a) honestly boy.
(The) head teacher didn't realize that he (was) absent.
(T)he man who wear(s) (a) blue T-shirt (might) be an athlete.

It seems that he is dishonest.

The head teacher didn't notice that he was absent. 或者 The head teacher is unaware of his absence.

The man who is in blue must be an athlete.

It seems that…
The head teacher did not realize that he was…
The man who wears blue t-shirt should be…