「私にとっては、レベルが低い生徒に英語を教えるほうが難しい。細かい説明が必要だから。だからといって、レベルが高いほうが簡単だとは言い切れないけどね。」これを自然な日常英語会話に訳してみたのですが、こんな感じで通じます？
For me, the lower level students are, the more difficult to teach English, because we have to teach more detail, however, I can’t say that the higher lever students are easy.

For me, it is troublesome to teach English to students who have less capability in English.
However, I am doubtful that it is more easy to teach English to those who have higher capability.

どうでしょうか？＞先輩方 　

It is hard to teach English to begginer for me, because i need to teach them many details. But i do not believe it is easy to teach to students who have studied for a long time.

なんか堅苦しいですよね、、、
　

but, even though, although, neverthelessなどは２つの相反する意味の文を繋げる接続詞なので、この場合は使うのは不適切だと思います。

It’s hard for me to teach English to beginners because I have to teach details and it is not easy for me to teach English to advanced students, either.
あるいはシンプルに
It’s hard for me to teach English to neither beginners nor advanced students because I have to teach details.

日本語文に難しい理由が初心者の方にしかないので、不適切かもしれませんが。どうでしょう？

Go Canucks go!!! 　

自然な日常英語会話にということだったのでこんな感じではどうでしょう？

Its more difficult for me to teach English to beginners than advanced students since I have to teach them every single detail...well but that does’t mean its easy to advanced students though...