Thats my parents house
That's = that is / my parents' house - the house belongs to my parents
Heres the headteachers office.
Here's = here is / the headteacher's office (the office belongs to one headteacher)
This is the teachers room where all the teachers have their breaks.
teachers' room ( the room belongs to all the teachers) / teachers have their breaks - no apostrophes 'teachers' and 'breaks' are plural nouns
My friends have all got new phones
No apostrophes - 'friends' and 'phones' are plural nouns
My friends phones are all new (lots of friends)
friends' phones ( the phones belong to my friends) / no apostrophe 'phones' is a plural noun
My friends phone is the latest model. (one friend)
friend's phone (the phone belongs to my friend)
