The Intramuros, or citadel, is small enough to be walked around easily and the ramparts make an obvious point of reference. St Malo also offers an impressive aquarium, but Mr Broomhead's group prefers the bowling alley on duller days.
Across the Rance estuary, with its tidal power station, is Dinard, where the main attraction is the Saturday market packed with locals, holidaymakers and chic couples down from Paris in search of a bargain. Students can sample local produce and buy souvenirs to take home.
Down river is Dinan, a medieval town with cobbled streets, a castle and an impressive view of the river below. Craft shops here are probably too expensive for pupils but the staff will appreciate them and there is a lot to see.
On the coast, a favourite attraction is the Fort la Latte. Tony Curtis and Kirk Douglas clashed swords here in the film The Vikings. It's an impressive castle and the stories of red-hot cannonballs fired at passing ships compensates for the long walk down from the coach park.
Further along the coast is Cap Frehel, a high rocky peninsular. There's a lighthouse and an impressive view on a clear day and it's possible to walk between Fort la Latte and Cap Frehel along a clifftop path. The walk takes about two hours but party leaders should be aware that both Cap Frehel and the clifftop walk have unfenced and precipitous cliffs - not a place to let pupils wander about unsupervised.
Mont St Michel is definitely worth half a day. Like its counterpart St Michael's Mount in Cornwall, this is an abbey set on an island of granite that is cut off from the mainland at high water. The difference is in scale. A guided tour can be booked but most school groups allow the children to wander up the main street and explore the ramparts.
Children like it for the cheap and tacky souvenirs, says Mr Broomhead. Stories of galloping horses being overtaken by the incoming tide are also popular and tales of the quicksand surrounding the island, said to have swallowed German tanks in the last war, prevent the easily bored from wandering too far.
A visit to Mont St Michel can be combined with a trip to Foug res, or to the zoo and adventure playground at Chateau de la Bourbansais. Some groups visit the mount on the return journey to the ferry.