young lady,
there is nothing wrong to 鍾意咗嗰男老師 !
However, PLEASE don't 同佢表白! because You should NOT mess around with the person you like ....
表白 is just a way to reduce the single sided pressure on your side.
It does not meant anything .... it does not meant you will have HIM as BF or anything ...
Contrastly, he can stop avoiding you or report your case to principal (headmaster) and it can be so uncomfortable situation ...
Like you said, if he already has GF or so ... case is even worst ...
since he look at you as his student .... and I think he care about the JOB (as teacher) ... more than anything ....
so all you can do now is say NOTHING!!!! keep it in your heart ....
You can treat him good ... but as TEACHER .... nothing further ...
because you don't want to mess up his life ....
OK, after you graduate, while you both are no longer TEACHER-STUDENT relationship ...
then at that time, you can tell him once you are in love with him and admire him ...
at that time it is a FAIR deal ... = FRIEND-FRIEND relationship ....
who knows what can happen ?
BUT for now .... never do anything ... focus on the education and respect him ...
and respect yourself ...
good luck :)
參考: Helped so many female/male teachers to handle similar situation.