Very difficult to prove a negative, but Buzzfeed tried.
This picture of Theresa May allegedly talking about the need to curb "the promotion of lesbianism in Merton's schools" went incredibly viral over the weekend despite little evidence she actually said it.
Actually, "little" is an exaggeration. The only evidence they found was that actual tweet.
Without any substantial evidence that she did say it, it seems only fair to assume she didn't say it.
Also, it seems implausible that in 1992 a politician would make such a mock-worthy statement and there would be no record of it.
Finally, given that there is no record of it, how would the person who made the meme know about it?
Edit: a commenter emphasizes that "there is no online record of it". In response to that, see here for how a slander from 30 years earlier could be exposed by information that was supposedly not available online.