Technology offers rich opportunities for learning across different physical and virtual spaces. However, most of current across-spaces proposals are either highly teacher-centered, inflexible in the students' self-management of learning artifacts during the enactment, or allow the teacher little/no control of such students' management of artifacts. Moreover, these proposals tend to be disconnected from the practices and tools that are usual in the classroom. How can we achieve a middle ground between keeping the teacher in control of across-spaces situations and, at the same time, providing students with a degree of flexibility to manage learning artifacts? Aiming to address such a challenge we propose the notion of learning bucket, and the Bucket-Server, a system implementing such a notion. A learning bucket is a container of learning artifacts which are generated and/or accessed across-spaces by the students during the enactment, according to constraints configured by teachers at design time. The responsive evaluation conducted, based on a feature analysis and a pilot study with experts, suggests that learning buckets can help evolve from teacher- to student-centered approaches, while maintaining the teacher in control of students' actions. The evaluation also indicates that the Bucket-Server surpasses the support provided by alternative proposals to across-spaces learning.