You sit down, open your notes, and within ten minutes you are somewhere else. Reading the same line twice, glancing at your pocket, thinking about lunch.
Many people experience this, and some of what contributes to it can be changed. Here is what the research does and does not say.
How long can students focus in class?
There is no honest single number, and it is worth being wary of anyone who gives you one.
What can be said is that attention on a single screen tends to be short in modern life. Gloria Mark, a researcher at UC Irvine, measured average attention on a single screen before switching at about 47 seconds in her recent studies. That is not a measure of lectures, but it describes the habit many of us may bring into a classroom: a mind used to switching every minute or so.
So if a lecture feels long, it may be partly because the rest of your day involves frequent changes of input.
Source: Gloria Mark, Attention Span (2023).
Does having my phone nearby really matter?
In one study, yes, even when you are not touching it.
Ward and colleagues (2017) tested people on working-memory and fluid-intelligence tasks. People did best with their phone in another room and worst with it on the desk, with pocket or bag in between. This held even when the phone was silenced and unused, and the effect was larger for people who were more dependent on their phones.
Later replications found smaller or mixed effects, so treat this as one study and not a law. Still, "phone in another room" costs you nothing to try.
Source: Ward, Duke, Gneezy & Bos, "Brain Drain," Journal of the Association for Consumer Research, 2017.
Are notifications the problem?
They may be part of it.
An observational study of real-life smartphone use found that about 89% of smartphone interactions were started by the user, not prompted by a notification.
That said, notifications do cost something. Fournier and colleagues found that social media notifications during a focus task caused a brief slowdown in processing, and the size of the effect tracked notification volume and checking habits more than total screen time.
So silencing the phone is worth trying, but it may not be enough on its own. Keeping the phone out of reach is a simple extra step.
Source: Heitmayer & Lahlou, Computers in Human Behavior, 2021; Fournier et al., "Attention hijacked," Computers in Human Behavior.
Is short-form video making it harder?
It may be linked, though the evidence is correlational.
A 2025 meta-analysis in Psychological Bulletin pooled 71 studies and about 98,299 people. Heavier short-form video use was linked to poorer attention and, most strongly, poorer inhibitory control, which is the ability to stop yourself doing the easy thing. It was also linked to more stress and anxiety.
Correlational means we cannot say the videos cause the focus problem; the link could run in either direction. Even so, if a lecture feels slow after an hour of clips, this is one thing worth noticing.
Source: Nguyen et al., Psychological Bulletin, 2025.
Does switching between tasks wear down focus?
It is associated with worse focus.
Ophir, Nass and Wagner (2009) found that heavy media multitaskers performed worse on task-switching and filtering tests than light multitaskers. That is an association, not proof that multitasking causes the difference.
The practical reading is simple. If you have a laptop open with chat and a tab for something else beside your notes, it is easy to split your attention, so closing them is worth trying.
Source: Ophir, Nass & Wagner, PNAS, 2009.
Could sleep be part of it?
It may be.
A 2025 meta-analysis in Frontiers in Psychiatry covered 21 cohort studies and 548,338 people. Each extra hour of daily screen time was associated with a bedtime about 13.2 minutes later, roughly 3 to 5 minutes less sleep, and higher odds of difficulty falling asleep.
Sleep is easy to skip over, and these figures are associations, not a measure of what happens in class.
If you have ADHD, sleep is also worth knowing about. One 2025 perspective in Frontiers in Psychiatry reports sleep problems in up to 80% of adults with ADHD, delayed sleep timing in up to 78% of children with ADHD, and melatonin onset about 45 minutes late in children and about 90 minutes late in adults. Its recommendations include morning light and limiting evening light, screens included. If you are worried about your sleep or attention, a doctor is the right person to ask.
Source: He et al., Frontiers in Psychiatry, 2025; Luu & Fabiano, Frontiers in Psychiatry, 2025.
Can two weeks without phone internet help?
One randomised trial suggests it may.
Castelo and colleagues (2025) blocked mobile internet on the smartphones of 467 participants for two weeks. Sustained attention improved by an amount comparable to about 10 years of age-related decline, alongside better mental health and well-being. Calls and texts still worked, and increased nightly sleep was one mechanism.
You do not need to block everything to take something from this. It suggests that attention can improve over a period as short as two weeks.
Source: Castelo et al., PNAS Nexus, 2025.
How can I focus better in class and school?
None of these are proven classroom interventions. They follow from the research above and from plain common sense.
- Put the phone out of reach. In your bag, in another room if you can, not on the desk.
- Do one thing at a time. Notes only, no side tabs, no chat window.
- Protect your sleep. Screens off earlier, and morning light if you can get it.
- Expect the wobble. If your mind drifts, notice it and return. Drifting is normal; returning is the skill.
- Take a real break between classes. Walk or look out of a window instead of switching to a feed.
The short version
Trouble focusing in class is common and often has several contributing factors: a phone within reach, a habit of switching, and too little sleep, with short-form video and multitasking also linked to poorer attention. Most of the evidence is correlational, but one randomised trial found attention improved after two weeks without mobile internet.
Start with the cheapest change, the phone out of reach, and give it a week. You are not broken.