My school is having two new classrooms built. They started at Easter and it was still going on at the end of term. I don't know if it's finished not now.
It caused huge disruption. The biggest being that we couldn't use the playground at all for the entire summer term. It was used as the access point and vehicles and people were back and forth the whole time. It was noisy and can you imagine trying to teach a lesson whilst there is a mini digger right outside the window!
We had to have staggered playtimes so that the children could be outside on a strip of grass which was the only outdoor space left. Then the school had to pay for the lunchtime staff to be there for longer.
The whole school had to use a side door to come in and leave the building so we lost teaching time ferrying children back and forwards instead of being able to use the nearest door. Assembly was pushed back ten minutes for example to accommodate this. That's fifty minutes a week lost which is a whole lesson. That's your whole time for art.
About four times the water was cut off and we had no toilets. In a primary school! This affected the school lunches as well.