Gender: boy
Mendel Sendowski born in 1923 is the only result that fits for the the school range of 1921-1927 so I believe this is him. Also, I think he is the brother to Rachela Sendowska and Josef Sendowski because they are close in age and share the same address of Krauter 13 1.
Becoming stuck, I began searching for other family members with the last name Sendowski/Sendowska. I came across a Bajla Sendowska DOB 1894 with the same address Krauter 13 1. Also, I came across a Chil Sendowski DOB 1895 also with the same address Krauter 13 1. I believe these two may be the parents of these children given their age and similar addresses.