be proficient at

Early Development of Emerging and English-Proficient Bilingual Children at School Entry in an Australian Population Cohort.
How many polysomnograms must sleep fellows score before becoming proficient at scoring sleep?
Becoming proficient at explaining the standards
Proficient at Piano?
L1 mediation in L2 writing within groups of lowproficient students at tertiary level
An Integrated Technique Based on Level Set Balloon Force and Laplacian Algorithm for Proficient Analysis of Stem Cell Segmentation
Helping Students Become Proficient at Solving Fundamental Engineering Problems through Practice - The Homework Laboratory
PROFICIENT ZERO™ Wireless Music System Debuts at CEDIA EXPO 2011
Becoming Proficient at Explaining the Standards: Every Teacher Should Be Able to Explain to Students: "This Is What You Need to Know...
At or Above Proficient: The Reporting of NAEP Results in the Internet Age 1,2