In a school setting, the best person to assess the need and put this into place is the Occupational Therapist. They are usually the experts in sensory processing and are a font of great ideas to try.
So what does this look like in practice? It's different for each student since each has their own unique sensory needs. Typically, though, there is a break and sensory activities scheduled every 45 minutes to 2 hours, but again, this varies between students. Students can choose their activity or it can be chosen for them.
All of my students have breaks in their day where they can choose an activity, and we have an assortment of sensory aids available at all times if the student needs it or requests it. Some of these items are headphones, fidgets, weighted vests and blankets, joint compression, squeezes, rocking chair, body sock, light-up and spinning toys, etc, just to give you an idea.
I have a schedule in place for 3 of my students. One student does heavy work twice a day, and receives squeezes and tickles at least twice a day. His heavy work consists of sweeping, stacking chairs, and moving furniture. He is in love with cleaning up and stares at our custodial staff with wonder in his eyes at lunch time. He will on occasion help them after he has eaten his lunch. He usually reorganizes our calm area where we have a sofa, a comfy chair, a rocking chair, and a thick, fold-able floor mat. Then he stacks all the chairs in our room. As a result of these activities, he has relaxed enough to spontaneously greet people, something he wasn't doing before.
Another student has many gross motor/ oral input activities built into his schedule multiple times a day. Typically, he enters the classroom, does a few minutes of work, receives a food reward, then has either a quiet time where he falls asleep, or he has a gross motor activity. He has difficulty sleeping at home and he often comes to school not having slept the night before. His gross motor consists of walks around the perimeter of our school and/or time on the trampoline in our sensory room. If he needs calming activities, we take him to the sensory room and he gets onto our crash pad and we fold him in it, or into a sleeping bag in our tent area, or he lays on a mat and we roll a ball over his body.
In the quiet area in our room, he gets his hair brushed and his joints compressed. Once he is calm, we do another work activity followed by a food reward. We repeat this throughout the day, and as needed.
A third student has silly putty at all times when his hands are not otherwise occupied with work.
He has a tendency to have meltdowns at 9:30, so we are now scheduling a sensory room break at 9:00, where he lays in the crash pad.
He also has a schedule of activities he can choose from at 11:15 when he goes to PE. Shortly after that, he goes home. These activities have helped limit some aggressive behavior.
Typically, these activities last for about 15-20 minutes but it really depends on the student.
These have all worked wonders for my students and the overall level of negative behavior has reduced tremendously as a result of these interventions. If you've never done this, I would highly recommend consulting with the OT and setting some activities in place.