In special education, knowing how students learn and why they struggle is key to writing strong IEPs. One area that often gets overlooked is the difference between acquisition deficits and performance deficits. These terms may sound similar, but they mean very different things. And understanding them can completely change how we support our students, both academically and behaviorally.
Together, let’s breaks down what acquisition and performance deficits are, how to tell the difference, what evaluations may be used, and what strategies help support students through both. Whether you’re new to IEPs or a seasoned special education teacher, this is a topic you’ll want to feel confident about because the right support starts with the right understanding.
What Is an Acquisition Deficit?
An acquisition deficit means that the student does not yet know how to do something. The skill hasn’t been learned, taught, or mastered. It could be a reading strategy, a math process, or a social skill, but the key is that the student lacks the skill or doesn’t have the knowledge yet.
Students with acquisition deficits often don’t improve simply by being told to “try harder.” They need direct instruction, modeling, guided practice, and repeated opportunities to learn. For example, if a student doesn’t understand how to add fractions, no amount of redirection or motivation will fix it until the skill itself is taught in a clear, scaffolded way.
What Is a Performance Deficit?
A performance deficit means that the student has the skill, but does not use it consistently. The student has learned it, but for some reason, they are not showing it in the classroom. The barrier might be motivation, environment, attention, or even emotional regulation.
Performance deficits often show up when a student does something well in one setting (like with a para or during a pull-out session) but struggles in another (like during whole group instruction). It’s not a matter of can’t, it’s a matter of won’t or not right now… and it’s often unintentional on the student’s part.
The main difference between an acquisition and performance deficit is skill development. If the skill isn’t there at all, it’s an acquisition deficit. If the skill is there but it is inconsistent, it’s a performance deficit.
Both types of deficits can affect academic work, behavior, and social skills. Both can cause frustration – for the student and the teacher. And both require support and intervention. The goal is not just to identify what the student is struggling with, but why the struggle is happening.
When Are These Deficits Evaluated?
Acquisition and performance deficits are usually considered during the special education evaluation process, especially in areas like behavior, executive functioning, and academic progress.
A Functional Behavior Assessment (FBA) is often used to determine whether a behavior is an acquisition or performance issue. For example, is the student acting out because they don’t have the coping skills (acquisition), or are they choosing not to use them in certain situations (performance)?
Academic assessments like curriculum-based measures, diagnostic reading inventories, and dynamic assessment tools can also help reveal whether the student truly lacks a skill or just isn’t applying it.
Evaluations and Instructional Strategies That Can Help
Students with acquisition deficits need clear, direct instruction. Teach the skill step-by-step and use visuals, repetition, and modeling. Guided practice is essential. Make sure the student has many chances to try the skill with support before expecting independence. You’ll also want to break skills down into smaller parts, or chunk them. Use errorless teaching and immediate feedback. Make practice predictable, and revisit skills regularly so the learning sticks.
For acquisition deficits, look for evaluations that measure specific skill mastery. These might include standardized academic tests, criterion-referenced tests, or diagnostic assessments in reading, writing, or math.
For performance deficits, the focus is on prompting, motivation, and generalization. Remind the student to use the skill, build it into routines, and offer reinforcement when the student uses the skill in the right situation.
Use visual cues, checklists, or timers to help prompt the behavior. Teach the student to self-monitor or reflect on when they used the skill and what helped them succeed, and practice the skill in a variety of settings so it becomes more automatic (this also promotes generalization of the skill).
For performance deficits, you’ll want to gather data across settings and situations. Behavior rating scales, classroom observations, executive functioning checklists, and interviews with multiple staff members can help paint a picture of when and where the student demonstrates the skill… and when they don’t.
Sometimes, both deficits can exist together. A student might need to learn a skill and also learn when and how to use it.
No matter what kind of deficit a student has, your job as an IEP team member is to support progress. That means identifying the root issue, selecting the right interventions, and monitoring how well those supports are working. Make sure IEP goals reflect the student’s actual needs. If the issue is acquisition, goals should target teaching the missing skills. If it’s a performance issue, goals may need to focus on generalization, prompting, or environmental supports.
Understanding the difference between acquisition and performance deficits helps IEP teams avoid jumping to conclusions or using the wrong intervention (this is also why data analysis is so important!). It helps us write better goals, collect better data, and support our students more effectively.
When we take the time to figure out why a student isn’t making progress, we can do something about it… and that’s where the real power of special education lives. Whether you’re in your first year or your fifteenth, keep asking: is this a skill that needs to be taught, or one that needs to be used more often? That simple question can change everything.
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