A student joins a lesson from one place: their Lessons tab. When the teacher clicks Start Lesson, an invite appears there and the student clicks Join Lesson. Nothing else in the app is a way in — the Schedule shows when lessons are planned, and a classroom card is the teacher’s side of the room.
If a student cannot see the lesson, one of three things is true. The teacher has not started it yet — the invite only exists once they click Start Lesson. The student is not connected to that teacher — without the teacher code, the student isn’t attached to the teacher at all, and the teacher won’t see them in their student list. The code is normally entered at sign-up; a student can add or fix it any time in their account under Profile → the Teacher code field, where it can be entered or changed. Or the teacher started a classroom link room rather than a lesson with that student — a link room is joined through its link and sends no invite; to reach a specific student, start from the student list.
For teachers: starting from Students → Start Lesson next to the student’s name is the direct route and works whether or not the lesson is on the schedule. Scheduling is optional. If recurring lessons are emailing students every week, leave them off the schedule and start each one from the student list when it is time.
What to check, in order: is the lesson started; is the student on Lessons (not Schedule); is the teacher code set in the student’s account; was it started from the student list rather than a link room.