Yotsubato - translations

Hi, I bought the first Yotsubato manga and I'm confused about how the following quote is used. I know what the words mean, but I can't work out what he is trying to get across:

After yotsuba asked if there was a festival (kyou wa matsuri ka!?), her father replies - ''gakkou da gakkou''. Gakkou is 'school', obviously, but can someone explain why he says it like that?

Also, there is a phrase the father says, following the 'gakkou da gakkou' which I half understand:

''zou iya ashita kara natsuyasumi da naa'' - I understand that tomorrow is the summer holidays, but I don't see what ''zou iya'' means. I know iya means 'no' but I don't see how it would fit in with the sentence.

I hope you can help, thanks in advance :)

I don't have that manga, so I can't be completely sure about these translations. But, I think when the father is saying ''gakkou da gakkou'' he's saying something like: "School. You have school (today)." The second "gakkou" being used for emphasis. Could the latter sentence be "sou iya"? If so, it's the same as "sou ieba" which means "which reminds me" or "now that you mention it".

Thank you for your response :)

I just checked and it is 'sou iya'. What a stupid mistake on my part -_-