This is a great activation to model for the students and depending on where your students are at it can be a great activity for them to practice with each other. To release the gift of tongues:

Have the person place their hand on their own stomach.
Place your hand on the person’s hand.
Pray that (just as Jesus said) out of this person’s belly would flow rivers of living water.
Coach the person through the process of learning to speak in tongues.

Often people need a little help learning how to speak in tongues. It is a different type of speech – you’re not speaking what your head is telling you, you’re speaking what your spirit is telling you. Learning how to rewire to speak from a different place is a little tricky. Often people will hear a specific phrase in their head or feel a sensation in their mouth or on their lips as the Spirit is activating the gift. Encourage them to speak out whatever they hear or feel they should say. It may feel strange, but the gift of tongues is a little strange!

Once people are activated they will probably need to practice the gift regularly. I encourage people to try and pray in tongues five minutes a day for a while after they’ve received the gift, this will help establish them in how to flow in the gift.