The school said the move was due to a "health and safety issue" but expected it to reopen in the "very near future".
Ofsted said it could not disclose its concerns until the inspection ended.
It added it had "made some findings and shared them with the principal". The second day of the inspection is taking place later.
In a statement on the school`s website titled "short term closure", interim principal Stuart Wilson said: "Owing to a health and safety issue, I have taken the decision to close the school... until I am confident that all children are safe on site.
"As parents, you will be informed directly, and on the website, when you are able to send your children back to school...
"Assuring you that we have your children`s best interests at heart."
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