Lead was ripped from a school roof in Maidenhead while teachers held a parents' evening beneath.
The thieves are believed to have struck at St Luke's School sometime between 8-8.30pm on Tuesday last week.
The Cookham Road primary has ordered artificial lead to repair the damage.
A pile of lead was later found dumped over a nearby fence.
Top Ten Articles
The Met Office has issued a yellow alert for Windsor and Maidenhead, Slough and Wokingham, warning that rain moving eastwards across the south of the country may turn to snow in some places.