It would depend on the context.
We had the day off because it was our teacher's training day (only one teacher was being trained)
The whole school was closed for teachers' training (more than one teacher was being trained)
There are three possible options for your question. If you are referring to more than one teacher, there is no apostrophe (teachers). If you are referring to an object that belongs to one teacher, the apostrophe is between the r and s (teacher's desk). If you are referring to an object that belongs to more than one teacher, the apostrophe is after the s (teachers' break room).
Depends, if the word "teachers" is a plural noun, and refers to multiple teachers then use an apostrophe. Example: The teachers' club handed out free pencils. If the world "teachers" is singular, and only refers to one teacher, then use an apostrophe like so: My teacher's dress is very red. If you are not referring to possession at all, and nobody is owning anything in the sentence, then put no apostrophe
Two teachers with Master's Degrees.
The apostrophe will come after s. (James')
Vidyasagar Teachers' Training College was created in 1968.
The apostrophe comes after "teachers" in plural possessive forms because it indicates that the possession is shared among the teachers. Placing the apostrophe before the "s" would suggest that only one teacher owns or possesses the item, not multiple teachers together.
The importance of teachers traning
If an apostrophe is after the "s" in a word, it typically indicates possession or ownership by multiple people or things. For example, "teachers'" means something belongs to multiple teachers.
Orvill E. Ault has written: 'The maverick' 'The training of special teachers' -- subject(s): Training of, Teachers, Special education teachers
If you're talking about something that belongs to the teacher, then you need the apostrophe. Teacher's desk, teacher's computer, etc. If you're talking about teacher as a plural noun, then you don't need the apostrophe.
George Ridding has written: 'Examination in theory v. normal schools as the training for teachers' -- subject(s): In-service training, Training of, Teachers
Homer Eber Cooper has written: 'Cost of training teachers' -- subject(s): Teachers, Training