But you shouldn't, since according to 61.1(b)(3)(iii)(A), it has to be more than 25 nm for a Sport Pilot student to log as XC.
That is not entirely correct. It must be more than 25NM to be used to fulfill the requirements of the rating, they can still log it as cross country.
For it to be cross country it simply needs to meet these 4 requirements.
(A) Conducted by a person who holds a pilot certificate;
(B) Conducted in an aircraft;
(C) That includes a landing at a point other than the point of departure; and
(D) That involves the use of dead reckoning, pilotage, electronic navigation aids, radio aids, or other navigation systems to navigate to the landing point.
The distance only comes into play when you are using it to meet the requirements for certain ratings. 25 NM for sport pilot, and 50 NM for Private, commercial, and instrument ratings. You can however use it for the 500 hours required for an ATP rating.