Schools and holidays do not necessarily explain the largest drop that occurred in the group aged 20-24 (the graph is the courtesy of James Ward on twitter @JamesWard73).
Here is an alternative view (from @michaeljswalker):
Recent drop is covid cases just shows that we have enough immunity that, absent mass events, and in presence of heatwave, R can fall below 1.
We will discover later this week whether bad weather and nightclubs (albeit with a little more immunity) will push above 1 again.
The trend from Northern Ireland over past week (increasing cases) shows that mass events might matter more than holidays and closed schools.