The indefinite pronouns one, anyone, everyone, and none are singular in number. They should, therefore, follow the rule that requires a singular subject to be used with a singular verb.
None of the students is able to read at grade level.
This rule is frequently disregarded by native speakers.
None of the students are able to read at grade level.
The Associated Press Stylebook, gives this rule regarding none (literally, “not one”):
none:
1. It usually means no single one. When used in this sense, it always takes singular verbs and pronouns: None of the seats was in its right place.
2. Use a plural verb only if the sense is no two or no amount: None of the consultants agree on the same approach. None of the taxes have been paid.
The practice of giving singular indefinite pronouns plural verbs has been going on for a long time in English. It may not be logical, but it is idiomatic.
