YOU SAID:
it's been a long time since i have been to school
INTO JAPANESE
私は学校に通って以来、長い時間を過ごしています
BACK INTO ENGLISH
I have been having a long time since I went to school
INTO JAPANESE
私は学校に通ってから長い時間を過ごしてきた
BACK INTO ENGLISH
I have been having a long time since I went to school
Come on, you can do better than that.