I did PCR's on my two youngest on thursday because they had slight coughs and there brother had tested positive the week before. We're still waiting for their results but based on when symptoms started it has been over 10 days since their symptoms started (started Christmas eve and took a while to get PCRs delivered) so finished their isolation period anyway. But I'm not sure if we can send them to school while waiting for PCR results even if it has been 10 days. Lateral flows are negative but their brothers was too even though he was positive 