Gender: boy
School:
School #20A
A search for H* Tarnowski turned up Henoch Tarnowski, whose first name sounds close to Heniek. Also, Henoch was the only one born in the right birthdate range for his school and to have signed the album.
The only other person with a matching address to Henoch's was Ruchla (b. 1901), who is probably Henoch's mother. They were both deported on March 20, 1942, during the month of daily deportations to Chelmno.