What?
You don't take an extra 5 days holiday - you use 5 days of your annual leave allocation to cover the inset days.
You'd use your annual leave allocation each year regardless of inset days or not.
Then I would have to then find cover for 5 days during the other school holidays instead.
5.6 weeks doesn't fit into 13 weeks no matter how you try.
If you take 2 weeks to cover Christmas Holidays, Two weeks for summer vacation and a week at Easter, where do you find the other week to cover the inset days.
And if you take the inset days as vacation, where do you fit in the lost week.
Far easier and practical to have the inset days on days that the school is already closed to children and that would save 5 days where you would either have to provide childcare, take holiday or take unpaid time off work. The actual school closures are already there, why add more.
For example, Half term runs from Monday to Sunday. I take a weeks leave to look after my young son. No problem. However an inset day is added to the Friday prior to the Half Term break, thus I have to take an extra days holiday to accommodate this, leaving me with one days less holiday the next time a school break comes along.
Now toward the end of the school year, I have taken my holiday entitlement, and due to the necessity of taking 4 periods of 4 weeks and 1 day, I only have 1 days holiday remaining, but there is another half term break to accommodate, what do I do, If the inset days had been included in the 13 weeks holiday that the Children get outside of term time I would still have enough holiday to take the full week, but as it is I would either have to take unpaid time, or pay for extra childcare.
Thus it is 5 days lost to me, my firm and the economy as a whole.