OneBookPlus
8.0#1 in tutoring center softwareFrom A$29 a monthFree planAndroidiOSWebAPI
VisitYou want what its maker publishes above — check its page for the details.
It suits independent tutors who want to manage students, lessons, scheduling, and payments in one web service. The free Starter plan is geared to tutors with up to five students and five sessions per month.