As others have said, I really wouldn't worry. They've missed so much I would think it would be expected that many are not meeting expectations.
At home I would just have fun - reading together, looking at pictures, pointing out some words.... one of our fav's was 'you choose' . And ask the teacher if they have any great game suggestions for Maths. But most importantly, don't stress, and try to have fun - that's the best way of learning x