My landings are far from perfect, but my instructor doesn't take over controls and help me flare.
Nor should he "help you"
Only one of you should be flying the aircraft.
Unless he is demonstrating the flare and you are following him through then only one of you should be with your hands on the control column.
Remember the instructor has to sign you off for an endorsement and it doesn't matter if you have a stage check - the person who does the stage check isn't going to sign you off they are.
Your instructor should be following a syllabus - ask to see it! (Although if doing a part 61 FAA PPL then there is no formal requirement for one - I would still ask for one)
21 hours isn't too bad either there are plenty of pilots who do way more than that to solo...
Regarding changing schools it can be difficult if your on a visa and not a US resident or citizen. If you provided more information then we could probably help out some more.