OP: unless you are much older than me (and with a kid in P2, I doubt it
), then the holidays you got - even at primary school were a week in October (they introduced the October Week when I was in primary school), c.2 weeks at Christmas, c.10 days at Easter, assorted long weekends and a slightly longer summer holiday.
My mum was a teacher and one of her bugbears was that English teachers didn't have as many teaching days as Scottish teachers.
As others have said, the INSET days have come out of the teachers' holidays.
You can see all the holidays, including the Inset days, for the following school year on your council web-site (Glasgow has had its dates up for ages)
Re your dd not being able to read: it is frustrating, but my ds wasn't reading during P1 (I kept on telling them that he wasn't "blending" - he was just learning the stories off by heart) - but they said that some kids just aren't ready developmentally until that are 6. As it was, he was 6.75 before he finally "got" it (that, despite 6 weeks extra 1:1 tuition at the beginning on P2 from the depute). But at 10 (P6) he is now free reading, back in the top group for language (since end of P4) - so sometimes it is just a matter of time.
I also happen to know that the teachers are equally frustrated by the fragmented April - but the May Weekend, together with the INSET days, is not a new thing.