Difference between using ころ and ころに？


I'm kinda new to this site so I'm not entirely sure how the format works.

In the sentence below, which I'm assuming I translated correctly as "When I
was in high school, I studied often":

> 高校のころ、僕は勉強した。

some people tend to add に after ころ when I looked it up. Is it necessary and is
it wrong to have/not have the に particle in the sentence? I'm fairly certain
that the に particle is used for destination/certain time reference among other
things but I don't see why it's more common to not have it at the end of ころ
while some people actually do

Also, I didn't know if I can include a separate question since I didn't really
want to make a whole new thread for it but is it wrong if I were to
say「高校でいるのころ」 instead of 「高校のころ」 to be more specific?




For the translation, I would say

> 高校のころ、僕はよく勉強していた。 (spoken)
>
> 僕が高校生だった頃はよく勉強していた。 (written)

  * You usually use 高校のころ when you're speaking.
  * よく勉強していた: Here, よく勉強する means study often, 勉強 has a duration so していた is better.
  * After 頃 , you usually use は or nothing.

You can use 頃に when you want to insist on the time context. Like:

> あの頃にあなたに会った。 (It's あの頃 that I met you)

or when it's the destination.

> あの頃に戻りたい。 (I want to go back to あの頃)




For the translation, I would say

> 高校のころ、僕はよく勉強していた。 (spoken)
>
> 僕が高校生だった頃はよく勉強していた。 (written)

  * You usually use 高校のころ when you're speaking.
  * よく勉強していた: Here, よく勉強する means study often, 勉強 has a duration so していた is better.
  * After 頃 , you usually use は or nothing.

You can use 頃に when you want to insist on the time context. Like:

> あの頃にあなたに会った。 (It's あの頃 that I met you)

or when it's the destination.

> あの頃に戻りたい。 (I want to go back to あの頃)

