It is recommended to all school participants to reserve their hotel in Leiden where the social dinner will take place and from where there is a direct and regular bus connexion to ESTEC (from the central station bus 30 and 230 end destination ESTEC).
Here are some hotel suggestions:
Close to the train station:
golden tulip https://leiden-centre.goldentulip.com/en-us
d'oude morsch http://www.hoteldeoudemorsch.nl/
Best western https://www.bestwestern.nl/booking-path/hotel-details/best-western-city-hotel-leiden-leiden-92723
More options: https://goo.gl/maps/RmoavuSVBqm