Translation:School is boring.
That means "to be bored". You use 심심하다 to express that you're feeling bored, and 지루하다 to express that something is boring, so if you said 학교는 심심해요 it would mean the school is bored.
I am a native speaker, and the translation can be both "학교는 지루합니다."and "학교는 심심하다."
For reference, 심심하다 does mean to be bored, and 학교 is not the subject in "학교는 심심하다."
심심해요 is bored. As in "I am bored bc im not doing anything." 지루하다 is more of a description that describes something that is boring.