CFI has this requirement:

§ 61.189 Flight instructor records.

(b) A flight instructor must maintain a record in a logbook or a separate document that contains the following:

(2) The name of each person that instructor has endorsed for a knowledge test or practical test, and the record shall also indicate the kind of test, the date, and the results.

(c) Each flight instructor must retain the records required by this section for at least 3 years.

Ground instructor doesn't. It is one small relief from record keeping.