There teacher-students ratio. Other studies like Bozzomo (1978),

There have
been series of inquiries about class size, but teacher-student ratio has not
been conducted as extensively as the former. Number of students per teacher is
generally associated with class size and it is mainly believed that smaller
classes provide a better teaching and learning. This belief has been shared by
many countries like the USA, European countries, China, Japan, and many other
countries and they made policies to reduce their class sizes. Amongst the OECD
countries, the average class size at the lower secondary level is 23. There are
countries like Finland, Iceland, the UK with class sizes of 19 and lower and
countries like Turkey, Korea and China with class sizes of 28, 34 and even 54; Blatchford
& Lai, OECD (as cited by Nizamettin Koca and Bekir Celika, 2015). According
to the available data online, Shanghai student-teacher ratio (junior high
school) fell gradually from 13.91 persons in 2005 to 11.49 persons in 20141.

ratio is assumed by many as class size; though they are related, they are not
accurately the same in nature. Class size is the number of students in a class
or, the total number of students in a classroom. Teacher-Student ratio is the number
of students per teacher, in other words the amount of students a teacher
teaches in a school (Graue & Rauscher, 2009). In schools with smaller
teacher-student ratio, teachers can have extra time to spend with each student
and review their improvement and also provide a greater individualized teaching
that accommodates each student (Johnson, 2011). Schools with larger class size
and high teacher-students ratio recorded poor performance while better academic
performance is associated with schools with small size and lower
teacher-students ratio. Other studies like Bozzomo (1978), Bourice (1986) and
Bolton (1988) confirm that there was no relationship between the size of the
class and the results. 

The empirical
evidence on teacher-student ratio (T-S ratio) is mixed. In fact, several
studies conclude that there are no effects of T-S ratio on student achievements.
However, there are also compelling findings demonstrating a positive effect of
increased T-S ratio on student learning, especially for low achievers and
students from lower socioeconomic backgrounds, see for example, Falch, Sandsør,
& Strøm; Hoxby; Leuven & Løkken, Blatchford, Bassett, Goldstein, &
Martin; Finn & Achilles; Fredriksson, Öckert, & Oosterbeck, Buckingham,
Wheldall, & Beaman; Fien et al.; Vaag Iversen & Bonesrønning (as cited
by O.J. Solheim et al., 2017).