[Grammar] on/at/by my own choice.

[Aamir Tariq]

Suppose, I used to work at a school as a teacher but I decided to quit my job for some reason. Now a colleague of mine from the same school is asking me to rejoin the school. And I am saying no.

1. I left the school at my own choice.
   
2. I left the school on my own choice.
   
3. I left the school by my own choice.

Now tell me which one is grammatical and which one is more natural.

Regards
Aamir the Global Citizen

 

[GoesStation]

Number three is the only grammatical and natural choice.

 

[emsr2d2]

I find 3 unnecessarily wordy.

I left school by choice.
I chose to leave school.
I left school. It was my choice.

 

[Aamir Tariq]

All right, If I rephrase my question a little bit by replacing "my choice" by "my own free will" then which preposition will be appropriate?

1. I left the school at my own free will.
   
2. I left the school on my own free will.
   
3. I left the school by my own free will.

Will it still be the third?

 

[emsr2d2]

Yes. 1 and 2 don't work.

 

[GoesStation]

I think of my own free will​ would be most common. Perhaps that's in AmE though.

 

[emsr2d2]

As happens sometimes on this forum, I read what I expected to read. I could have sworn that 3 said "of".