The phrase "are less proficient" is correct and usable in written English.
It can be used to compare the skill levels of different individuals or groups in a specific area or task.
Example: "Students who do not practice regularly are less proficient in mathematics than their peers who study consistently."
Alternatives: "have lower proficiency" or "are not as skilled".
Evidence supports that girls are less proficient than boys at performing ball skills.
They are no less talented than West Ham but are less proficient at the mechanics of securing a result.
It is important to accurately measure FMS competency in adolescent populations, particularly in girls, who are less proficient than boys.
The test showed that American students are less proficient in history than in any other subject over all.
The students with parents who are less proficient in English will feel frustrated and possibly embarrassed, causing tension and wasting time and energy.
As with fluent speakers, team members who are less proficient in the language must always confirm that they have been understood.
This would be especially interesting for the case of Taiwan Min because speaker gender generally covaries with language proficiency and females tend to be less proficient in Min than males (Huang and Fon 2007).
Studies show that men tend to be less proficient than women at discerning fake from genuine laughter.
He also loved golf, but was less proficient with woods and irons than with knights and bishops; friends who had been humbled at chess were quick to remark, "Did he tell you about his golf game?" GARY H. LEE The Incurable Collector Bayonets.
Moreover, these capacities appear to trade off: if you're adept at focusing on details located in the center of the visual field, which is key to reading, you're likely to be less proficient at recognizing features and patterns in the broad regions of the periphery.
