Bogus sexual abuse

Teacher, first put the matter before Principal and explain what really happened and invite the girls for mutual talks.

How you are sure that the teacher's version is correct?

@P.Venu Ji, How you sure that his version is not correct?? Being a law expert, the focus should be to suggest legal way and not to judge right and wrong.
@Sini- First don't panic, especially if u are innocent. It's ok, nowadays courts are very careful while dealing cases related to Woman molestation.
For me I see some misunderstanding, (possibly, any unconscious action/touch of yours, may have offended that girl), so try to resolve this matter with help of staff/principal with parents of the student. Although if things getting out of control, don't waste time, In such case, strongly recommended to seek personal advice of any good local advocate and discuss for anticipatory bail meanwhile.  Be mentally prepared. 
To file and win Defamation case- first you need to get a clean chit from the court (that in case if this drama gets dragged till that level), only thereafter you can file for it.