Sorry, there was no way football was played as far up as Sacred Heart school. There is no evidence, either historically or geographically to support it. On a map it looks feasible, as soon as you stand on where it has been claimed you would nope out, as would any sane referee!
Growing up on Granville terrace (as was) all the old codgers claimed the pitch was between Rovers Street (built post 1890 move to Ewood) and the Leamington Pub. It's flat enough and "a stones throw from the meadows" as the 1920s rovers history claims it to be.