Gwent Police say the 15-year-old girl from Newbridge was arrested on suspicion of threats to kill, possession of a bladed article on a school premises and conspiracy to commit murder.
The 14-year-old girl from Risca was arrested on suspicion of conspiracy to commit murder.
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The Electoral Commission has released ten top tips to help the public through the process of voting on Thursday.
Winds will strengthen throughout the morning, with a risk of coastal and inland gales.
Becoming windy with heavy rain approaching Tuesday.