Conditional past-future

 I had a situation today when a student did not turn up for his lesson.(11.00-11.45) A student in a later lesson (11.50-12.35) then tried to say - "If you had known he wasn't coming to his lesson you would go home early" This means I would have gone home at 13.20 instead of 14.30. But this sentence did not sound right to me. We wanted to talk about the future (going home) linked to the past. "If I had known he wasn't coming to the lesson I would go home early" - I would prefer the following "If I had known he wasn't coming to the lesson I COULD go home early" Does anyone have any thoughts on this?

Many thanks

Opti 

Hi, welcome to englishforums.
I don't understand your example, because I don't quite understand the context. Anyway, let's suppose you can arrange the schedule however you want, so that if a student doesn't show up you, can go on and then go home earlier. In that case, I would say it's ok to say something like:
If you had known that student wouldn't show up and you hadn't waited for him, [you would go home earlier today / you would have left earlier today / etc.]
I think it's perfectly ok to use "would + bare infinitive" or "would have + past participle" to refer to the future in cases like that. That's what would happen or would have happened... but it's actually not happening or not expected to happen.
I'm not a native speaker, by the way, so you might want to wait for the other members.

Then I think both "would" and "could" are correct!

Kooyeen: «I think you can use that sentence even if you have yet to go home, that same day. Or you could also just use "would", or just "could"... whatever you want, as long as it's conditional.»

Doesn't it depend on when the hypothetical going home happens? If it's in the past then "woud have" is required, and if it's in the future — "would go" is the only alternative... I just don't get how you allow two different conditinals describe the same situation...

Examples:
«If I had known that you wouldn't come I would now be o my way home»
(the hypothetical consequent is located in the Present)

«If I had known that you wouldn't come I would have got home already»
(The hypothetical consequest is in the past)

«If I had known that you wouldn't come I would be home in... (casts a look at the watch) five minutes, because I would have left ten minutes ago»
(First consequesnt is in the future and second — in the past)

Thanks guys for your welcome and your interest in helping with this one.

I will try to be a bit more specific.

If I had known he wasn't coming to the lesson - obviously when I said this I knew that he had not come

I would go/be going home earlier - I have not yet gone home (I still have some lessons to teach), but I would be able to go home early (earlier) had I known. As it was I didn't know so I didn't go home earlier.