1. A computer-implemented method of generating recitation items for assessing speaking proficiency, the method comprising: generating, using one or more processing systems, one or more text sets, wherein each text set is in a target language and includes one or more texts; extracting a target language phoneme distribution from a target language corpus that is in the target language; extracting a first native language phoneme distribution from a first native language corpus that is in a first native language of one or more users; extracting a second native language phoneme distribution from a second native language corpus that is in a second native language of one or more users; comparing the target language phoneme distribution to the first native language phoneme distribution to identify any first phoneme n-gram (i) whose frequency of appearing in the target language corpus satisfies a first predetermined criterion and (ii) whose frequency of appearing in the first native language corpus satisfies a second predetermined criterion, wherein any such identified first phoneme n-gram is included in a first list; and comparing the target language phoneme distribution to the second native language phoneme distribution to identify any second phoneme n-gram (i) whose frequency of appearing in the target language corpus satisfies a third predetermined criterion and (ii) whose frequency of appearing in the second native language corpus satisfies a fourth predetermined criterion, wherein any such identified second phoneme n-gram is included in a second list; determining, using the one or more processing systems, a value for each text set using one or more metrics that include a phonetic difficulty metric by: generating phoneme sequences for each text set; comparing the phoneme sequences with a phonetic challenge list that includes any phoneme n-gram appearing in both the first list and the second list; computing, based on the comparison, a respective phonetic difficulty value for each text set, and determining the value for each text set based on at least the respective phonetic difficulty value; and selecting, using the one or more processing systems, a final text set from the one or more text sets to serve as the recitation items for assessing speaking proficiency based on the values associated with the text sets.
1. A computer-implemented method of generating recitation items for assessing speaking proficiency, the method comprising: generating, using one or more processing systems, one or more text sets, wherein each text set is in a target language and includes one or more texts; extracting a target language phoneme distribution from a target language corpus that is in the target language; extracting a first native language phoneme distribution from a first native language corpus that is in a first native language of one or more users; extracting a second native language phoneme distribution from a second native language corpus that is in a second native language of one or more users; comparing the target language phoneme distribution to the first native language phoneme distribution to identify any first phoneme n-gram (i) whose frequency of appearing in the target language corpus satisfies a first predetermined criterion and (ii) whose frequency of appearing in the first native language corpus satisfies a second predetermined criterion, wherein any such identified first phoneme n-gram is included in a first list; and comparing the target language phoneme distribution to the second native language phoneme distribution to identify any second phoneme n-gram (i) whose frequency of appearing in the target language corpus satisfies a third predetermined criterion and (ii) whose frequency of appearing in the second native language corpus satisfies a fourth predetermined criterion, wherein any such identified second phoneme n-gram is included in a second list; determining, using the one or more processing systems, a value for each text set using one or more metrics that include a phonetic difficulty metric by: generating phoneme sequences for each text set; comparing the phoneme sequences with a phonetic challenge list that includes any phoneme n-gram appearing in both the first list and the second list; computing, based on the comparison, a respective phonetic difficulty value for each text set, and determining the value for each text set based on at least the respective phonetic difficulty value; and selecting, using the one or more processing systems, a final text set from the one or more text sets to serve as the recitation items for assessing speaking proficiency based on the values associated with the text sets. 18. The method of claim 1 , wherein the one or more metrics include a prosody distribution metric by: generating prosodic annotations for each sentence in each text set; extracting prosodic patterns from the prosodic annotations; determining a prosodic distribution from the prosodic patterns; and comparing the prosodic distribution with an ideal prosodic distribution and computing a respective prosodic distribution similarity value; wherein determining the value for each text set is based on at least the respective prosodic distribution similarity value.