Sandwich structures are widely used in lightweight engineering applications due to their high stiffness-to-weight ratio and structural efficiency. With the advancement of Additive Manufacturing (AM), the integration of complex lattice architectures as cores in sandwich beams has become increasingly viable, enabling the fabrication of highly optimized structures with fewer manufacturing steps and improved performance [1]. The present study investigates the bending response of sandwich beams with additively manufactured lattice cores and composite facesheets under three-point bending. The structures under consideration consist of cross-ply CFRP facesheets and an LPBF-fabricated AlSi10Mg lattice core of f2ccz topology. An analytical model founded upon the First-Order Shear Deformation Theory (FSDT) has been developed in order to predict deflection and stress resultants [2]. In addition, finite-element (FE) simulations (ANSYS) have been performed for both non-homogenized (explicit lattice) and homogenized (orthotropic-equivalent) cores. The present study investigates the impact of core aspect ratio and facesheet-core thickness ratio on global stiffness, normal stress, and transverse shear. The findings demonstrate a high degree of congruence between FSDT and FE for global deflection and bending stresses across the examined cases, thereby substantiating the appropriateness of FSDT for lightweight AM lattice-core beams in three-point bending. The homogenized core has been shown to efficiently reproduce the global response with a reduced computational cost. In contrast, the explicit lattice reveals local stress concentrations at strut intersections, which are important for failure assessment. The analysis under discussion highlights the dominant role of core shear in compliant cores and provides practical guidance on when homogenized modeling and FSDT are sufficient, and when detailed lattice-resolved FE is required for integrity checks.