Two of the most intense albums I know of are the Staple Singers' "Uncloudy Day" issued in 1959 and "Will The Circle Be Unbroken" from 1960 [Wikipedia says it was released in 1969, but that's wrong].
Both are collections of earlier recordings, some dating from the Staples' first session for Vee Jay in November 1955.....when Mavis Staples would have been 16 years old.
A version of "So Soon" was definitely recorded at that 1955 session. Whether it was re-recorded for release on this 45 is unknown to me.
Of course it doesn't really matter if Mavis was 16, 17, or 18 at the time. The recording is extraordinary no matter what. In fact, it's close to unearthly. If there was ever a singer who's voice qualifies as a force of nature, it's Mavis Staples.
If any of ya'll don't own a copy of the Staple Singers Vee Jay recordings, then you should def seek out the 'twofer' of "Uncloudy Day" and "Will The Circle Be Unbroken". Yep, they come packaged together. To my mind, they're essential albums.
Hope ya'll enjoy......