My children went to a school with a roll of just over 20 children in two classrooms. One teacher had P1, P2, p3, the other had P5, p6, P7. P4 went into the smaller of the two. It worked very well and I felt my children did very well there. At one point, the numbers went down to 18 and not much prospect of increase so one teacher had to leave. That left the head teacher to teach all seven years in one room with visiting teachers to do art, music and PE. We started to worry that it would close completely. The children already had to travel 7 miles each way into the next village for school and would have had a much longer journey over hills that were sometimes closed in bad weather so we relieved when more families moved into the village. When we left the island, the roll had gone up to 31 - the most it had been in years.
Incidentally, when I told my family that we were moving to Scotland, my then SIL, a teacher in England, said that they would get a good education as the Scottish system was better than the English.