If you are younger than 26 years and you use the train regularly or once in a while, the NMBS offers several options to travel at a reduced tariff.
If you come to the campus by train on a daily basis then the Student Season Ticket is probably the cheapest option. After choosing the route (e.g. Leuven-Brussels) and the validity period (1, 3 or 12 months) you can travel on that route unlimited, during the week and/or the weekend, within the validity period.
If you do not come to the campus every day then the Student Multi (Campus) is the ideal solution for you. The price of the card depends on the distance between the campus and your home/student accommodation, but it is always cheaper than a Go Pass. You can use the campus card 5 times for the same route, between two Belgian railway stations, within 49 calendar days.
In order to receive a Student Season Ticket or Student Multi, you need to submit your identity card and a school certificate at the train station. As such the card for your season ticket will be processed.
If you are younger than 26 years and you want to visit Belgium by train, but you have a tight budget, then you can use the Go Pass. With this card you and your friends can travel to any Belgian railway station and the card is valid for 1 year. The Go Pass contains 10 single journeys that cost € 6,60 per journey to any destination in Belgium.
If you are older than 26 years, you will have to pay the regular fares as there is no student discount anymore. Check the website of the NMBS to find out about the cheapest fares.