There is significant difficulty in learning to spell in a second language with complex orthography, particularly where the students are raised bilingually and have had only limited exposure to the written form of the target language. Such students require tailored remedial work on orthography, which is disruptive for the teacher to organise during class. We have devised a system for students to practice spelling individually through an online tool, which tests for the students' performance on individual rules of spelling and adapts to test the rules the student is weakest at. We illustrate the application of the tool to Russian.