'I have studied at high school for 2 years' or 'I studied at high school for 2 years'

[trueheart_205]

Should I say 'I have studied at high school for 2 years' or 'I studied at high school for 2 years'?
And my studying is in the past, not continuing to present. Sometimes I see the present perfect and simple past are used interchangedly. So, how can I distinguish them?
Thanks in advance.

[Chicken Sandwich]

NOT A TEACHER

I have studied at a high school for two years. You may or may not be still studying at a high school.

I studied at a high school for two years. This happened in the past and I am no longer studying at a high school.

I have been studying at a high school for two years. This implies that I have not yet finished studying at a high school.

I hope this helps.