"There are so few students in the intermediate class so it's difficult to take a day off."
"There maren't any students in the intermediate class so I feel bad if I miss a lesson."
"There are so few students in the intermediate class so it's difficult to take a day off."
"There are so few students" 「生徒の人数が少ない」
"the intermediate class" 「中級クラスは」
"so ~" 「なので〜」
"it's difficult to ~" 「〜にくい」
"take a day off" 「休み」
"There aren't many students in the intermediate class so I feel bad if I miss a lesson."
"there aren't many students" 「生徒の人数が少ない」
"I feel bad ~" 「[〜して申し訳ない](https://eikaiwa.dmm.com/uknow/questions/132450/)」・「〜しにくい」
"if I miss a lesson" 「休み」
I feel bad taking a day off from my intermediate class because there are only three of us in the class.
I feel kind of guilty missing one of my intermediate level English classes because it's just myself and two others in the class.
この場合、次のように言うと良いですよ。
ーI feel bad taking a day off from my intermediate class because there are only three of us in the class.
「中級クラスには私たち３人しかいないから、クラスを休みにくい」
I feel bad ~ing で「〜するのが申し訳ない・〜しにくい」
intermediate class で「中級クラス」
ーI feel kind of guilty missing one of my intermediate level English classes because it's just myself and two others in the class.
「中級英語クラスには私と他２人しかいないから、休むのが気がひける」
I feel kind of guilty ~ing で「〜する気がひける・うしろめたい」
intermediate level English classes で「中級英語クラス」
ご参考まで！
オーストラリア 
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