YOU SAID:
mr. lau and his class are dumb
INTO JAPANESE
氏。ラウと彼のクラスは愚かな
BACK INTO ENGLISH
Mr. Lau and his class are stupid
INTO JAPANESE
ラウ氏と彼のクラスは愚かです
BACK INTO ENGLISH
Mr. Lau and his class are stupid
That didn't even make that much sense in English.