According to Vygotsky, a range of task too difficult for the child to do alone but possible with the help of adults and more skilled peers is called:

'Lev Vygotsky', a Soviet psychologist, has propounded the "Socio-cultural Theory". This theory implies the idea that social interaction plays a crucial role in the development of learners' cognitive ability. 

According to Vygotsky, 'zone of proximal development' or 'ZPD' refers to the:

• the gap between what the child can do independently and with assistance.
• difference between what a learner can do on his/her own and what he/she can do with someone's help.
• range of tasks too difficult for the child to do alone, but possible with the help of adults and more skilled peer.

• distance between learners' actual development level and his/her level of development under someone's guidance.

Additional Information

Other Important Terms Proposed by Vygotsky in his 'Socio-cultural Theory':

• Scaffolding: It refers to a process through which temporary support is imparted to the learners to enhance learning to achieve goals.
• More Knowledgeable Other(MKO): It refers to a person with a higher skill level and a better understanding of the concepts than the learners.

Hence it could be concluded that according to Vygotsky, a range of tasks too difficult for the child to do alone but possible with the help of adults and more skilled peers is called Zone of Proximal Development.