学校にいた is how you say I was at school in Japanese.
It is 'ni juu yon' in Japanese.
As you say in your question, a four-year LPN program lasts four years.
gakko no kamoku
去年 /kyo nen/ means 'last year' in Japanese.
?
'Gakunen no hajimari WA kugatsu de WA nakute, shigatsu desu.'
Nyūsatsu no gakkō
"[watashi ha] yonsai desu."
yo hoy no de
ni juu yon
As a noun, "year" is 'toshi' in Japanese.