C# Online Compiler | .NET Fiddle

using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;

public static class MyExtensions
{
	public static IEnumerable<IGrouping<TKey, TSource>> ChunkBy<TSource, TKey>(this IEnumerable<TSource> source, Func<TSource, TKey> keySelector)
	{
		return source.ChunkBy(keySelector, EqualityComparer<TKey>.Default);
	}

	public static IEnumerable<IGrouping<TKey, TSource>> ChunkBy<TSource, TKey>(this IEnumerable<TSource> source, Func<TSource, TKey> keySelector, IEqualityComparer<TKey> comparer)
	{
		const bool noMoreSourceElements = true;
		var enumerator = source.GetEnumerator();
		if (!enumerator.MoveNext())
		{
			yield break;
		}

		while (true)
		{
			var key = keySelector(enumerator.Current);
			var current = new Chunk<TKey, TSource>(key, enumerator, value => comparer.Equals(key, keySelector(value)));
			yield return current;
			if (current.CopyAllChunkElements() == noMoreSourceElements)
			{
				yield break;
			}
		}
	}

	private class Chunk<TKey, TSource> : IGrouping<TKey, TSource>
	{
		private readonly ChunkItem _head;
		private readonly object _mLock = new object ();
		private IEnumerator<TSource> _enumerator;
		private bool _isLastSourceElement;
		private Func<TSource, bool> _predicate;
		private ChunkItem _tail;
		public Chunk(TKey key, IEnumerator<TSource> enumerator, Func<TSource, bool> predicate)
		{
			Key = key;
			_enumerator = enumerator;
			_predicate = predicate;
			_head = new ChunkItem(enumerator.Current);
			_tail = _head;
		}

		private bool DoneCopyingChunk {
			get{
				return _tail == null;
			}
		}
		public TKey Key
		{
			get; set;
		}

		public IEnumerator<TSource> GetEnumerator()
		{
			var current = _head;
			while (current != null)
			{
				yield return current.Value;
				lock (_mLock)
				{
					if (current == _tail)
					{
						CopyNextChunkElement();
					}
				}

				current = current.Next;
			}
		}

		IEnumerator IEnumerable.GetEnumerator()
		{
			return GetEnumerator();
		}

		private void CopyNextChunkElement()
		{
			_isLastSourceElement = !_enumerator.MoveNext();
			if (_isLastSourceElement || !_predicate(_enumerator.Current))
			{
				_enumerator = null;
				_predicate = null;
			}
			else
			{
				_tail.Next = new ChunkItem(_enumerator.Current);
			}

			_tail = _tail.Next;
		}

		internal bool CopyAllChunkElements()
		{
			while (true)
			{
				lock (_mLock)
				{
					if (DoneCopyingChunk)
					{
						return _isLastSourceElement;
					}

					CopyNextChunkElement();
				}
			}
		}

		private class ChunkItem
		{
			public readonly TSource Value;
			public ChunkItem Next;
			public ChunkItem(TSource value)
			{
				Value = value;
			}
		}
	}
}

public static class Program
{
	public static void Main()
	{
		var list = new List<Data>{new Data("01/21/2017", "Math", "Pass"), new Data("06/02/2017", "Science", "Pass"), new Data("05/31/2018", "Math", "Fail"), new Data("06/28/2018", "Science", "Pass"), new Data("07/03/2018", "Math", "Pass"), new Data("07/19/2018", "Science", "Fail"), new Data("08/01/2018", "Math", "Fail"), new Data("09/13/2018", "Science", "Fail"), new Data("09/15/2018", "Math", "Fail"), new Data("10/01/2018", "Science", "Fail"), new Data("12/15/2019", "Math", "Pass"), new Data("10/11/2019", "Science", "Fail"), new Data("01/21/2017", "Math", "Pass"), new Data("06/02/2017", "Science", "Pass"), new Data("05/31/2018", "Math", "Fail"), new Data("06/28/2018", "Science", "Pass"), new Data("07/03/2018", "Math", "Pass"), new Data("07/19/2018", "Science", "Fail"), new Data("08/01/2018", "Math", "Fail"), new Data("09/13/2018", "Science", "Fail"), new Data("09/15/2018", "Math", "Fail"), new Data("10/01/2018", "Science", "Fail"), new Data("12/15/2019", "Math", "Pass"), new Data("10/11/2019", "Science", "Fail"), new Data("08/01/2018", "Math", "Fail"), new Data("09/13/2018", "Science", "Fail"), new Data("09/15/2018", "Math", "Fail"), new Data("10/01/2018", "Science", "Fail"), new Data("12/15/2019", "Math", "Pass"), new Data("10/11/2019", "Science", "Fail"), new Data("10/11/2019", "Science", "Fail"), new Data("01/21/2017", "Math", "Pass"), new Data("06/02/2017", "Science", "Pass"), new Data("05/31/2018", "Math", "Fail"), new Data("06/28/2018", "Science", "Pass"), new Data("07/03/2018", "Math", "Pass"), new Data("07/19/2018", "Science", "Fail"), new Data("08/01/2018", "Math", "Fail"), new Data("09/13/2018", "Science", "Fail"), };
		var query = list.GroupBy(x => x.Test).Select(x => new
		{
		x.Key, Results = x.ChunkBy(p => p.Result).Select(y => new
		{
		y.Key, Count = y.Count()}

		).Where(z => z.Count > 1)}

		);
		foreach (var item in query)
		{
			Console.WriteLine("Group key = " + item.Key);
			foreach (var inner in item.Results.Where(x => x.Key == "Fail"))
			{
				Console.WriteLine(" - " + inner.Count + " consecutive fail tests or (" + inner.Count + "-1) = " + (inner.Count - 1) + "  sequential fails ");
			}
		}
	}

	public class Data
	{
		public Data(string examDate, string test, string result)
		{
			ExamDate = examDate;
			Test = test;
			Result = result;
		}

		public string ExamDate
		{
			get;
			set;
		}

		public string Result
		{
			get;
			set;
		}

		public string Test
		{
			get;
			set;
		}
	}
}

        var list = new List<Data>{new Data("01/21/2017", "Math", "Pass"), new Data("06/02/2017", "Science", "Pass"), new Data("05/31/2018", "Math", "Fail"), new Data("06/28/2018", "Science", "Pass"), new Data("07/03/2018", "Math", "Pass"), new Data("07/19/2018", "Science", "Fail"), new Data("08/01/2018", "Math", "Fail"), new Data("09/13/2018", "Science", "Fail"), new Data("09/15/2018", "Math", "Fail"), new Data("10/01/2018", "Science", "Fail"), new Data("12/15/2019", "Math", "Pass"), new Data("10/11/2019", "Science", "Fail"), new Data("01/21/2017", "Math", "Pass"), new Data("06/02/2017", "Science", "Pass"), new Data("05/31/2018", "Math", "Fail"), new Data("06/28/2018", "Science", "Pass"), new Data("07/03/2018", "Math", "Pass"), new Data("07/19/2018", "Science", "Fail"), new Data("08/01/2018", "Math", "Fail"), new Data("09/13/2018", "Science", "Fail"), new Data("09/15/2018", "Math", "Fail"), new Data("10/01/2018", "Science", "Fail"), new Data("12/15/2019", "Math", "Pass"), new Data("10/11/2019", "Science", "Fail"), new Data("08/01/2018", "Math", "Fail"), new Data("09/13/2018", "Science", "Fail"), new Data("09/15/2018", "Math", "Fail"), new Data("10/01/2018", "Science", "Fail"), new Data("12/15/2019", "Math", "Pass"), new Data("10/11/2019", "Science", "Fail"), new Data("10/11/2019", "Science", "Fail"), new Data("01/21/2017", "Math", "Pass"), new Data("06/02/2017", "Science", "Pass"), new Data("05/31/2018", "Math", "Fail"), new Data("06/28/2018", "Science", "Pass"), new Data("07/03/2018", "Math", "Pass"), new Data("07/19/2018", "Science", "Fail"), new Data("08/01/2018", "Math", "Fail"), new Data("09/13/2018", "Science", "Fail"), };
 
using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
​
public static class MyExtensions
{
    public static IEnumerable<IGrouping<TKey, TSource>> ChunkBy<TSource, TKey>(this IEnumerable<TSource> source, Func<TSource, TKey> keySelector)
    {
        return source.ChunkBy(keySelector, EqualityComparer<TKey>.Default);
    }
​
    public static IEnumerable<IGrouping<TKey, TSource>> ChunkBy<TSource, TKey>(this IEnumerable<TSource> source, Func<TSource, TKey> keySelector, IEqualityComparer<TKey> comparer)
    {
        const bool noMoreSourceElements = true;
        var enumerator = source.GetEnumerator();
        if (!enumerator.MoveNext())
        {
            yield break;
        }
​
        while (true)
        {
            var key = keySelector(enumerator.Current);