請問: "你總是告訴我現在上課到哪一頁，當我遲到的時候" 用英文怎麼說，用過去式，感謝您!?

You always came to my rescue and told me what page we were on, when I arrived late.

You always came to my rescue to tell me
what page(of text)
we were on
when I arrived late.
The past tense with the form of a verb used to express actions in the past are:-
came, to tell(=told), were, arrived.

When I was late, you always told me which page the teacher was talking about.

You always told me which page we were studying , when I was late for class.

你的講法有點"奇怪"句法和文法，假如照著寫是

You always told me on which page of textbook the lesson was at, when(ever) I was late.

我會寫成whenever以表達"每次當我遲到時"而不是如你原句表達"單/某一次)，希望是你想表達的意思。

"你總是告訴我現在上課到哪一頁，當我遲到的時候"==While I was belated into the classroom and then you said what page was read. Yip