Early-childhood education has undergone a change in recent years, shifting its emphasis from literacy to STEM, as well, the knowledge and skills necessary for effective preschool mathematics teaching have been given much attention in recent studies. Early-childhood teaching knowledge is a key factor in mathematics teaching, impacting future teaching-learning processes and students' achievements. The study presented in this article is part of broader research conducted among Preschool Para-Educators in Israel. In Israeli kindergartens, the educational staff consists of an academic teacher and a Preschool Para-Educator (PPE), who is a high school graduate. Despite their lack of academic background and training, the PPEs are required to deal with mathematics teaching in their everyday encounter with kindergarten children. Hence the need for a unique training program for PPEs, in order to provide them with basic knowledge for teaching Early-Childhood Arithmetic (ECA). One aim of the study was to show how teaching experience activities contribute to constructing the knowledge of teaching ECA in a specific content area: Numeracy Skills. As part of the training program, the participants were required to analyse videos, scenarios, and simulations. The study included 35 PPEs. Data collected from questionnaires and observations were analysed using a qualitative and quantitative mixed method. The results show that most PPEs internalized the knowledge learned throughout the course, applying it in simulation activities. The study confirms the assumption that PPEs need intensive training in ECA in order to refine their teaching skills, giving everyday arithmetic practice in kindergarten a more solid professional basis.