Design and computer graphics curricula for tertiary education include 3-D modeling skills. Students must learn to represent (complex) 3-D objects by means of parametric surfaces or polygonal meshes. Three-dimensional modeling may be a complex task, and students must be able to accrue a certain deal of experience in the field before passing the exam. The main difficulties the students must face mainly concern the comprehension of 3-D shapes and the choice of the most appropriate modeling techniques. This article proposes a framework to support bachelor's degree students in modeling 3-D objects by means of parametric surfaces. The proposed framework provides two augmented reality (AR) apps for smartphones and a web portal. The mobile AR apps allow students to deeply visualize 3-D object shapes, thus performing a set of guided exercises to practice basic modeling techniques. On the other hand, the web portal allows students to share their models with teachers and classmates to obtain feedback and comments. The preliminary results show the effectiveness of the proposed solution, as all volunteers involved in the experimental phase achieved better results after using the tools. Moreover, the students' opinions about the proposed framework are positive.