I will always prefer that a student practice on a piano vs a keyboard.
However, during the first year of piano, a keyboard is satisfactory to learn and costs are relatively low. Additionally, there are no piano tuning costs for that first year, and often, space is a factor, which makes keyboards a plus.
I do strongly encourage parents who have keyboards to make the transition to a piano by the end of the first year. The technical standard on a keyboard is not the same, as piano study and eventually, the technique will become an issue as the student advances. Yes, the instruments look the same, but they are not, in actuality. If, however, the keyboard you have at home is fully weighted, 88 keys, then I’m agreeable to this type of instrument.