Best cost effective way from Paris to Mont Saint-Michel for students?

It's a long day trip but you can take the train. You would take the train to Rennes and then the bus to MsM. The entire service is offered by SNCF to the bus and train schedules match up. Buy your tickets 90 days in advance for the cheapest fares.

How many students are we talking? Every trip I ever took in a academic setting took a bus. But if it's only a few, that's different.

If it's just you and a friend, and money is really tight, you could be better off both in time and cash to stay in Paris where there is always too much to do anyway.

I agree with all of the above.

How many students are we talking about? There are tour companies that do day trips from Paris to Mont St Michel. You might get special rates if your group is large enough. Google ParisVision or Viatour.

Thank you so much to everyone.