In a text message to parents on Monday the school said it was tracing those the confirmed case had been in contact with.
Adding that ‘50 Y9 students may be affected’ the text message read ‘each affected family will be contacted’.
The school says years 7, 8, 10 and 11 are not affected by the case.
Parents of Year 9 students were sent a text saying ‘all Y9s are to stay at home today while we do a track and trace’.
It read: “We will contact anyone who has to isolate further asap.”
A spokesperson for Outwood Academy Valley said on Monday that after one of their Year 9 students tested positive for Covid-19 the rest of the year were told to stay home as they traced contacts ensuring ‘all those who need to self-isolate are notified’.
He said "Our remote learning resources are available to all students – meaning those who do self-isolate do not miss out on their education.
"Despite our best efforts to go above and beyond the official guidance it was always inevitable issues would arise - but we will continue to ensure we minimise risk as far as is possible."
Today (Thursday) a spokesman added that the whole of Year 9 were not being kept home but there was ‘one isolated positive case’ and those identified as close contacts were self-isolating.
No further details were given regarding how many students had been identified as close contacts.