What is a simpler way to do the teacher stats code challenge?

# The dictionary will look something like:
# {'Andrew Chalkley': ['jQuery Basics', 'Node.js Basics'],
#  'Kenneth Love': ['Python Basics', 'Python Collections']}
#
# Each key will be a Teacher and the value will be a list of courses.
#
# Your code goes below here.

def num_teachers(d):
    return len(d.keys())


def num_courses(d):
    total_courses = []
    for value in d.values():
        for val in value:
            total_courses.append(val)
    return len(total_courses)


def courses(d):
    total_courses = []
    for value in d.values():
        for val in value:
            total_courses.append(val)
    return total_courses

def most_courses(d):
    courses_num_list = []
    teachers_list = []
    indexes = []
    all_indexes = []
    most_teachers = []

    for courses in d.values():
        courses_num = len(courses)
        courses_num_list.append(courses_num)
    for teachers in d.keys():
        teachers_list.append(teachers)

    count = 0
    for num in courses_num_list:
        if count == 0:
            high_val = num
            count += 1
        else:
            if num > high_val:
                high_val = num
            else:
                pass

    indexes = [index for index, value in enumerate(courses_num_list) if value == high_val]
    for i in indexes:
        index = i
        most_teachers.append(teachers_list[index])

    for i in most_teachers:
        return i

def stats(d):
    teacher = []
    courses = []
    list_of_lists = []
    for key in d.keys():
        teacher.append(key)
    for value in d.values():
        courses.append(len(value))

    for num in range(0, len(teacher)):
        list_within = [teacher[num], courses[num]]
        list_of_lists.append(list_within)

    return list_of_lists