Hello there! Based on your needs, I would recommend MagicSchool AI. This tool offers an "Advanced Proofreading" feature that can identify writing issues in students' assignments and provide constructive feedback. This feature could be used to scan and edit your report cards for grammar and spelling errors.
Moreover, MagicSchool AI is designed to be user-friendly with an intuitive interface, which should make it easy for you to navigate and use. Currently, it's free for teachers, making it a cost-effective solution for your needs.
Please note that while Pedagogical and Gradescope are excellent tools, they do not specifically mention a grammar and spell-checking feature in their descriptions. Therefore, MagicSchool AI seems to be the most suitable option for your requirements.