There would have to be a very narrow definition of "lie" for this to not qualify:

"Correct lessson iss to follow ssteps laid down for you by older and wisser Sslytherin, tame your wild impulssess.”

Also, besides doubling the s's, EY denotes Parseltongue with violations of English grammar. This sentence is missing "the" at the beginning, the sentence "Will not sspeak of planss beyond thiss" lacks a subject, etc. If the "no lies" rules depends on precise parsing, it's odd that the grammar is so lax. If this is supposed to represent just a loose translation into English, and the "no lies" rules applies to the precise wording, rather than the general meaning, then we can't really know what's true.